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DEPARTMENT OF THE ARMY FIELD MANUAL
105-mm HOWITZERM52 SELF-PROPELLED
DEPARTMENT OF THE ARMY * DECEMBER 1956AGO 2790C-Nov
FM 6-77
FIELD MANUAL I DEPARTMENT OF THE ARMYNo. 6-77 WASHINGTON 25, D. C., 11 December 1956
105-mm HOWITZER M52, SELF-PROPELLED
Paragraphs Page
CHAPTER 1. INTRODUCTION--_________. 1-4 4
2. ORGANIZATION ______-___ 5, 6 8
3. SECTION DRILL
Section I. General _________--------- _ 7, 8 10II. Preliminary commands and 9-14 11
formation.
CHAPTER 4. PREPARING HOWITZERFOR FIRING ANDTRAVELING
Section I. Preparations for firing-______ 15, 16 19II. Preparations for traveling___ 17, 18 20
CHAPTER 5. DUTIES IN FIRING,INDIRECT LAYING
Section I. General --_--_____--------- 19, 20 21II. Duties of chief of section_---- 21-36 22
III. Duties of gunner ____---_-- _ 37-46 28IV. Duties of cannoneers and
driver. 47-73 35
CHAPTER 6. FIRING BY DIRECTLAYING
Section I. Technique of fire____________ 74-82 44
AGO 2790C 1
Paragraphs Page
Section II. Duties of chief of section…____ 83-91 53III. Duties of remainder of sec- 92-97 56
tion.
CHAPTER 7. TECHNIQUES AND SITU- 98-108 59ATIONS THAT REQUIREATTENTION
8. BORESIGHTING ANDBASIC PERIODICTESTS
Section I. General _____________------ 109, 110 70II. Boresighting __________----. 111-115 71
III. Basic periodic tests --------- 116-126 80
CHAPTER 9. MAINTENANCE AND 127-131 85INSPECTIONS
10. DECONTAMINATION OF 132-135 88EQUIPMENT
11. DESTRUCTION OF EQUIP- 136-139 91MENT
12. SAFETY PRECAUTIONS__ 140-143 93
13. TRAININGSection I. General _____________------ 144-147 96
II. Minimum training schedule___ 148-150 98
CHAPTER 14. TESTS FOR QUALIFICA-TION OF GUNNERS
Section I. General ________________-__ 151-158 102II. Test, direct laying, direct fire 159-163 105
telescope.III. Test, indirect firing, deflection 164-168 107
only.IV. Test, displacement correction_ 169-173 111V. Test, measuring deflection____ 174-178 113
VI. Test, laying for elevation, ele- 179-183 115vation counter.
2 AGO 2790C
Paragraphs Page
Section VII. Test, laying for elevation, 184-188 116gunner's quadrant.
VIII. Test, measuring elevation____ 189-193 117
IX. Test, measuring site to mask__ 194-198 118
X. Tests and adjustment of 199-206 120sighting and fire controlequipment.
XI. Test for materiel ______----- 204-208 123
APPENDIX REFERENCES -------.--. .------- 126
INDEX________ ------------------- ------- ------- 130
AGO 2790C 3
CHAPTER 1
INTRODUCTION
1. Purpose and Scope
This manual is a guide to assist commanders indeveloping the sections of 105-mm howitzer M52,self-propelled, firing batteries into efficient smooth-working teams that have a sense of discipline whichwill impel them to operate effectively under thestress of battle. This manual prescribes individualduties and section drills, inspection and maintenancedrills, and tests and adjustments for sighting and firecontrol equipment, and provides instructions for thedecontamination and destruction of equipment.
2. Definitions and Terms
a. Section. Tables of organization and equipmentprescribe the personnel and equipment comprisingeach section of a battery (figs. 1 and 2). In thismanual the term section is often used to designateonly the personnel required to serve one piece and itsequipment.
b. Front. The front of a section is the direction inwhich the muzzle of the howitzer points.
c. Right (Left). The direction right (left) is theright (left) of one facing the front.
d. In Battery. A howitzer is said to be in batterywhen the recoiling parts are in the normal firingposition.
4 AGO 2790C
Figure 1. 105-mm howitzer M52, self-propelled,and section personnel.
3. Description of Equipment
To avoid accidents caused by exceeding the capa-bilities and limitations of the motor carriage, allmembers of the section should be familiar with theperformance charcteristics shown in figure 3. Forfurther details pertaining to full-track vehicle capa-bilities and combat driving, see TM 21-306.
4. References
Publications pertaining to the 105-mm howitzerM52, self-propelled, and auxiliary equipment, cov-ering related matters which are not discussed in de-tail in this manual, are listed in the appendix.
AGO 2790C 5
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St
6 AGO 2790C~~~~
ll 1_ * --- - =-1I 18' 10" Jl 1 I0' 7"-*---1
TURNING RADIUS, PIVOT ROAD CLEARANCE 19sa"
SPEED 25 MPH SRIDGE CLASS30 TON
FORDING TRENCH
DEEPTH 48'/TL
- LE = i330_
Figure S. 105-mm howitzer M52, self-propelledperformance characteristics.
AGO 2790C 7
CHAPTER 2
ORGANIZATION
5. Composition of Section
a. The section consists of section personnel, a 105-mm howitzer M52, self-propelled, and auxiliaryequipment (fig. 1).
b. The personnel of the howitzer section are-(1) A chief of section (CS).(2) A gunner (G).(3) An assistant gunner (No. 1).(4) Four cannoneers, numbered from 2
through 5.(5) A motor carriage driver (D).
c. Section equipment is listed in appropriate SNLand TOE 6-317R.
6. General Duties of Personnel
a. Chief of Section. The chief of section is thenoncommissioned officer in command of the sectionand, as such, is responsible to the battery executivefor-
(1) Training and efficiency of personnel.(2) Performance of duties listed under section
drill, duties in firing, tests and adjustmentof sighting and fire control equipment, andinspection and maintenance of all section
8 AGO 2790C
equipment including the performance ofscheduled preventive maintenance serviceon motor carriage.
(3) Observance of safety precautions.(4) Preparation of field fortifications for pro-
tection of equipment, ammunition, andpersonnel.
(5) Camouflage discipline; local security; andchemical, biological, and radiologicalsecurity discipline.
(6) Maintenance of the weapon record book.(7) Police of the section area.
b. Gunner. The gunner is the assistant to thesection chief in carrying out the duties specified in aabove. The gunner's specific duties are prescribed inthe appropriate chapters of this manual.
c. Cannoneers. Cannoneers perform duties aslisted in this manual and any other duties that thechief of section prescribes.
d. Driver. The driver's primary duty is drivingthe motor carriage (TM 21-306) and performingpreventive maintenance on the vehicle. He also per-forms such other duties as prescribed by this man-ual, by TM 9-717A, or as may be assigned by thechief of section. These duties can include substitut-ing for any member of the section in firing.
AGO 2790C 9
CHAPTER 3
SECTION DRILL
Section I. GENERAL
7. Objective
The objective of section drill is the attainment ofefficiency: maximum precision coupled with highspeed.
8. Instructions
a. Adherence to the drills prescribed is necessaryto develop maximum efficiency and to prevent injuryto personnel and damage to equipment. Section drillmust be conducted in silence except for commandsand reports. The section must be drilled until re-actions to commands are automatic, rapid, andefficient.
b. Errors are corrected immediately. Each mem-ber of the section must be impressed with the im-portance of reporting promptly to the chief of sec-tion any errors discovered before or after the com-mand to fire has been given. The chief of sectionwill report errors immediately to the executive.
c. Battery officers supervise the drill to insure thatinstructions are carried out and that maximumefficiency is obtained.
d. Personnel should be rotated during training sothat each member of the section can perform all the
t0 AGO 2790C
duties within the section. In addition, battery over-head personnel not assigned specific duties duringdrill periods should be trained in the fundamentalsof section drill in order that they will be capable offunctioning efficiently with a howitzer section if re-quired.
Section II. PRELIMINARY COMMANDS AND FORMATIONS
9. To Form Section
a. To Fall In. The chief of section takes his post.On the command of execution the section forms in asingle rank at close interval, centered on and facingthe chief of section at a distance of 3 paces (fig. 4).Higher numbered cannoneers, if present, form inorder between No. 5 and the driver. The chief ofsection may indicate in his preparatory commandthe place and direction in which the section is toform. At the first formation for drill or exercisethe caution, "As section (s) ," precedes the command.The commands are FALL IN, or 1. IN FRONT(REAR) OF YOUR PIECE(S), 2. FALL IN, or 1. ONTHE ROAD FACING THE PARK, 2. FALL IN. Execu-tion is as follows: The section moves at double timeand forms at close interval, at attention, guidingon the gunner (fig. 4).
b. To Call Off. The section being in formation,the command is CALL OFF. At the command, allpersonnel in ranks, except the gunner, execute eyesright. The section then calls off in sequence, "Gun-ner," "1," "'2," "3," "4," "5," "Driver." As eachman calls out his designation he turns his headsmartly to the front.
AGO 2790C 11
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12 AGO 2790C
10. Posts of Section
The command is 1. CANNONEERS, 2. POSTS. Thecommand is general and is applicable whether thesection is in or out of ranks, at a halt, or marching.All movements are executed at double time and areterminated at the position of attention. Highernumbered cannoneers, if present, take posts as pre-scribed by the chief of section.
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Figure 5. Posts of section, dismounted.
AGO 2790C 13
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AGO 2790(] 1
a. Dismounted. The section moves to posts asshown in figure 5. All personnel are 2 feet outsidethe tracks and facing to the front.
b. Prepared for Action. The piece having beenprepared for action, posts are taken as shown infigure 6.
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Figure 6. Posts of section, prepared for action.14 AGO 27900C
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AGO 2790
c. Mounted, Not Prepared for Action. The sectionmoves to posts as shown in figure 7. Nos. 3, 4, and 5ride in another designated vehicle.
11. To Change Posts
To acquaint the members of the section with allduties and to lend variety to drill, posts should bechanged frequently. The section being in formation,the commands are 1. CHANGE POSTS, 2. MARCH, or1. SECTION CHANGE POSTS, 2. MARCH.
a. At the command 1. CHANGE POSTS, 2. MARCH,all number cannoneers except No. 5 (or the highestnumbered cannoneer) take two left steps, taking theposition of the next higher numbered cannoneer. No.5 moves at double time in rear of the section to thepost of No. 1. All other members of the section standfast.
b. At the command 1. SECTION CHANGE POSTS, 2.MARCH, the driver (or the leftmost man) movesat double time in rear of the section to the post of thegunner. The gunner and all the other men in linetake two left steps as in a above.
12. To Mount
The commands are 1. PREPARE TO MOUNT, 2.MOUNT, or MOUNT.
a. At the preparatory command, the sectionmoves at double time to positions shown in figure5. At the command of execution, all personnelmount. All personnel, except Nos. 3, 4, and 5, hastento positions as shown in figure 7. Nos. 3, 4, and 5do not mount the motor carriage. They move at
16 AGO 2790C
double time to the vicinity of a designated vehicleand mount it at the command of the driver.
b. If any members of the section are to remaindismounted, their designation is announced with thecaution, "Stand fast" given between the preparatorycommand and the command of execution. For ex-ample: 1. PREPARE TO MOUNT, "Driver stand fast,"2. MOUNT.
c. If the command is MOUNT, the section exe-cutes, without pausing, all that has been prescribedfor the command 1. PREPARE TO MOUNT, 2. MOUNT.
13. To Dismount
The commands are 1. PREPARE TO DISMOUNT, 2.DISMOUNT, or DISMOUNT.
a. At the preparatory command, all members ofthe section mounted in the motor carriage placethemselves in a position from which they may dis-mount easily. At the command of execution, mem-bers of the section dismount in inverse order ofmounting and quickly take posts as shown in figure5.
b. At the command DISMOUNT, the sectionexecutes without pausing all that has been pre-scribed for the command 1. PREPARE TO DISMOUNT,2. DISMOUNT.
14. To Fall Out
a. At Drill. When it is desired to give the per-sonnel a rest from drill or relieve them temporarilyfrom a formation or post, the command FALL OUT
AGO 2790C 17
is given. The command may be given at any timeand means that the section is to remain in thevicinity of the drill area.
b. When Firing. When firing has been suspendedtemporarily, but it is desired to have the section re-main in the vicinity of the motor carriage, thecommand FALL OUT is given. Men stand clearof the piece to insure that settings and laying re-main undisturbed. During these periods the chiefof section may direct the men to improve the posi-tion, to replenish ammunition, or to do other neces-sary work.
18 AGO 2790C
CHAPTER 4
PREPARING HOWITZER FOR FIRING ANDTRAVELING
Section I. PREPARATIONS FOR FIRING
-i5. General
The howitzers of a battery will ordinarily be putinto position individually under the direction of theexecutive and chiefs of section. A stake should bedriven into the ground at a point where the centerof each carriage is to be placed. Another stakeshould be placed in the direction of fire 50 to 100yards from the first stake, so that the driver of themotor carriage can point the tube at the far stake ashe drives the vehicle into position over the firststake. Each vehicle is halted at its proper place bythe chief of section. Hand signals for guiding thevehicle are found in FM 21-60 and FM 25-10 andare discussed in paragraph 108, this manual.
16. To Prepare for Action
a. The motor carriage being in position or ap-proaching it, the command is PREPARE FOR AC-TION. Duties of individuals are given in table I.Each man takes his post (fig. 6) upon completion ofhis duties.
b. The howitzer normally will be partially pre-pared for action before reaching the firing position.
AGO 2790C 19
The duties of the cannoneers in preparing for ac-tion are the same whether the howitzer is movingor halted, but only such operations as are practicableare carried out while moving. Immediately afterthe howitzer is established in position, preparationfor action is completed without further command.
c. If PREPARE FOR ACTION has not been or-dered before the howitzer is established in position,the command is habitually given by the chief ofsection as soon as the vehicle is halted in position. Ifpreparation for action is not desired, the caution,"Do not prepare for action" must be given.
Section II. PREPARATIONS FOR TRAVELING
17. March Order
To prepare to resume travel, the command isMARCH ORDER. Duties of individuals are listedin table II. Each man takes his post (fig. 7) uponcompletion of his duties.
18. To Resume Firing in Another Positiona. If firing is to be resumed shortly in another
position in which the howitzer must be immediatelyready to fire, the command MARCH ORDER is notgiven. When a displacement is ordered, only thoseoperations necessary for the movement of the motorcarriage and the security of equipment are per-formed.
b. If the command MARCH ORDER is givenwhile the equipment is partially prepared for travelas described in a above, the remaining operationspertaining to march order are completed.
20 AGO 2790C
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CHAPTER 5
DUTIES IN FIRING, INDIRECT LAYING
Section I. GENERAL
19. Instructions
The general instructions in paragraphs 7 and 8on the conduct of section drill apply equally to sec-tion drill in duties in firing by indirect laying. Forduties of the battery executive, see FM 6-40 andFM 6-140.
20. Duties of Individuals(table III)
In general, the duties of individuals in the sectionin indirect fire are as follows:
a. The chief of section supervises and commandshis section and is responsible that all duties of thesection are performed properly, all commands exe-cuted, and all safety precautions observed.
b. The gunner sets the commanded elevation anddeflection, lays the piece, and refers the piece.
c. No. 1 opens the breech, loads the piece, andfires the piece.
d. No. 2 receives prepared rounds from No. 3and passes them to No. 1.
e. No. 3 fuzes projectiles and sets fuzes.
AGO 2790C 21
f. No. 4 prepares charges.g. No. 5 removes ammunition from containers.h. The driver shifts carriage as directed by the
chief of section and assists No. 5 in removing am-munition from containers.
Section II. DUTIES OF CHIEF OF SECTION
21. List of Duties(Detailed description of duties, pars. 22-36.)
a. Indicates the aiming point to the gunner.b. Measures the site to the mask.c. Follows fire commands.d. Indicates when the piece is ready to fire.e. Gives the command to fire.f. Lays the piece for elevation when the gunner's
quadrant is used.g. Reports errors and other unusual incidents of
firing to the executive.h. Conducts prearranged fires.i. Records basic data.j. Observes and checks frequently the functioning
of the materiel.k. Assigns duties when firing with reduced per-
sonnel.1. Verifies the adjustment of the fire control
equipment.m. Checks, before they are replaced in their con-
tainers, all rounds not fired which have been pre-pared for firing.
22 AGO 2790C
n. Controls the movement of the motor carriage.o. Supervises use of ammunition.
22. Indicates Aiming Point to Gunner
When an aiming point is designated by the exe-cutive, the chief of section insures that he hasproperly identified the point in question. The chiefof section then indicates it to the gunner. If thereis any possibility of misunderstanding, the chief ofsection will turn the panoramic telescope until thehorizontal and vertical cross hairs are on the pointdesignated.
23. Measures Site to Mask
The command is MEASURE THE SITE TOTHE MASK. The chief of section, looking throughthe bore, directs the gunner in placing the tube insuch a position that the lowest element of the borejust clears the crest at its highest point in the prob-able field of fire. The gunner then turns the eleva-tion counter knob in the appropriate direction untilthe three elevation verniers line up. The chief ofsection reads the elevation from elevation counterand reports to the executive, "Sir, No. (so-and-so),site (so much) ."
24. Follows Fire Commands
The chief of section follows fire commands. Herepeats the commands as required.
25. Indicates When Piece' is Ready to Fire
When the executive can see arm signals made bythe chief of section, the chief of section will extend
AGO 2790C 23
his right arm vertically upward as a signal that thepiece is ready to fire. He gives the signal as soon asthe gunner calls, "Ready." When arm signals can-not be seen, the chief of section reports orally tothe executive, "Sir, No. (so-and-so) ready."
26. Gives Command to Fire
When No. 1 can see arm signals made by thechief of section, the chief of section will give thecommand to fire by dropping his right arm sharplyto his side. When his arm signals cannot be seen, hecommands orally, FIRE or NO. (SO-AND-SO),FIRE. The chief of section will not give the signalor command to fire until all cannoneers are in theirproper places.
27. Lays Piece for Elevation When Gunner's Quadrant is
Used
a. The command QUADRANT (SO MUCH) in-dicates that the gunner's quadrant is to be used. Inlaying for elevation, the gunner's quadrant is em-ployed only when the elevation counter is inoperativeor known to be inaccurate. The gunner's quadrantmay be specified for use with assault fire or on cer-tain destruction missions.
b. Quadrant 361.8, for example, is set on the gun-ner's quadrant as follows: The upper edge of theindex plate is set opposite the 360 mark of the grad-uated arc on the quadrant frame, and the micro-meter on the index arm is turned to read 1.8. Caremust be taken to use the same side of the quadrantin setting both the index plate and the micrometerknob.
24 AGO 2790C
c. The announced quadrant having been set onthe gunner's quadrant, the piece loaded, and thebreechlock closed, the gunner's quadrant is set onthe quadrant seat on top of the breech. The wordsline of fire must be at the bottom of the quadrantwith the arrow pointing toward the muzzle. Thechief of section must be sure to use the arrowwhich appears on the same side of the quadrant asthe scale which he is using. He stands squarelyopposite the side of the quadrant and holds it firmlyon the quadrant seat, parallel to the axis of the bore.It is important that he take the same position andhold the quadrant in the same manner for eachsubsequent setting, so that in each case he will viewthe quadrant bubble from the same angle.
d. The chief of section then directs the gunnerto elevate or depress the tube until the bubble is cen-tered, being careful that the last motion is in thedirection in which it is more difficult to turn thehandwheel. He cautions the gunner when the bubbleis approaching the center, in order that the final cen-tering may be performed accurately.
e. Special and calibration corrections will beadded algebraically at the battery fire directioncenter and commanded as NO. (SO-AND-SO),QUADRANT (SO MUCH).
28. Reports Errors and Other Unusual Incidents of Firingto Executive
If, for any reason, the piece cannot be fired, thechief of section promptly reports that fact to theexecutive and the reasons therefor; for example,
AGO 2790C 25
"Sir, No. (so-and-so) out, misfire." Whenever it isdiscovered that the piece has been fired with anerror in laying, the chief of section reports that factat once; for example, "Sir, No. (so-and-so) fired 40mils right." Whenever the gunner reports that theaiming posts are out of alinement with the sight andthat the misalinement is due to the displacement ofthe carriage, the chief of section reports that fact tothe executive and requests permission to realinethem. Likewise, he promptly reports other unusualincidents that affect the service of the piece.
29. Conducts Prearranged Fires
Whenever the execution of prearranged fires isordered, the chief of section conducts the fire of hissection in conformity with the prescribed data.
30. Records Basic Data
The chief of section records data of a semi-permanent nature in a notebook. This data includessuch information as minimum elevation; aimingpoints used and their deflections; prearranged fireswhen section data sheets are not furnished; safetylimits in elevation and deflection; number of roundsfired, with the date and hour; and calibration andspecial corrections when appropriate.
31. Observes and Checks Frequently Functioning ofMateriel
The chief of section closely observes the function-ing of all parts of the materiel during firing. Beforethe piece is fired, he makes sure that the recoil me-chanism contains the proper amount of oil; there-
26 AGO 2790C
after, he carefully observes the functioning of therecoil system. He promptly reports to the executiveany evidence of malfunctioning (TM 9-717A). Ifthe piece returns to battery with a shock, an over-supply of recoil oil is indicated; if the piece over-recoils or does not return to battery, an insufficientamount of recoil oil is indicated. Whenever theamount of reserve oil is less than that prescribed,the index on the indicator rod of the replenisher willindicate "fill."
32. Assigns Duties When Firing With Reduced Personnel
Whenever the number of personnel serving thehowitzer is temporarily reduced to below that indi-cated in this manual, the chief of section makes suchredistribution of duties as will best facilitate theservice of the piece. Loss of cadremen, various de-tails, and casualties will necessitate the sectionsoperating with a reduced number of personnel to theextent that it is almost normal for section membersto double up on duties. Around-the-clock firing re-quires the chief of section to divide the section intoshifts to provide for relief.
33. Verifies Adjustment of Fire Control Equipment
See TM 9-324A for detailed instructions on test-ing and adjusting sighting and fire control equip-ment.
34. Checks, Before They are Replaced in Their Containers,All Rounds Not Fired Which Have Been Preparedfor Firing
The chief of section personally checks all rounds
AGO 2790( 27
not fired that have been prepared for firing beforethey are replaced in their containers, to see that allseven powder increments are present in proper con-dition, that they are assembled in proper numericalorder, and that they are of the same lot number. Healso checks to see that the lot number on the projec-tile and cartridge case corresponds to the lot numberon the container.
35. Controls Movement of Motor Carriage
When it is necessary to move the motor carriage,the chief of section instructs the driver to start theengine. He then controls the displacement of themotor carriage by voice, interphone, or hand signals.
36. Supervises Use of Ammunition
The chief of section supervises control and use ofproper lot numbers of ammunition as directed bythe battery executive.
Section III. DUTIES OF GUNNER
37. List of Duties(Detailed description of duties, pars. 38-46.)
a. Centers the level bubbles on the panoramictelescope mount.
b. Lays the piece for direction.
c. Alines the aiming posts, assisted by No. 5.
d. Lays the piece for elevation.
e. Sets a common deflection to a common aimingpoint after the piece has been laid.
28 AGO 2790C
f. Sets or changes the deflection.
g. Signals and/or calls "Ready."
h. Refers the piece.
i. Makes corrections for aiming post displace-ment.
38. Centers Level Bubbles on Panoramic Telescope Mount(fig. 8)
The gunner centers the level bubbles on the tele-scope mount by operating the leveling knobs as partof preparing the sight for action. Once the bubblesare leveled, it should not be necessary to make fur-ther adjustments during firing. However, the levelof the mount is verified before calling "Ready."
39. Lays Piece for Direction
(fig. 9)The piece being in position, tube in center of tra-
verse, and not laid for direction, the executive com-mands NO. (SO-AND-SO) ADJUST, AIMING.POINT THIS INSTRUMENT. After the gunnerhas reported "Sir, No. (so-and-so) aiming pointidentified," the executive commands NO. (SO-AND-SO) DEFLECTION (SO MUCH). The gunnersets the commanded deflection on the coarse azi-muth scale, as viewed through the window, and themicrometer scale. He then directs the driver tomove the motor carriage until the vertical line ofthe sight reticle is approximately on the executive'saiming circle. The gunner then traverses the tubeuntil the vertical line of sight is exactly on the exe-cutive's aiming circle. He checks to insure that the
AGO 2790C 29
E~~~~~LEVAflON ~ ~
iI
LEVELINGELEVATIM "MOCHAN
LEVEUNGEL^ 0 0 P _ PRV ADJUSTINGN
' iFigure 8. Telescope mount T179.
bubbles are level and announces, "Sir, No. (so-and-so) ready for recheck." As additional deflectionsare announced by the executive, he sets them on thecoarse azimuth and the micrometer scales and tra-verses the tube so that the vertical line of sight is on
30 AGO 2790C
COARSE AZIMUTHSCALE
AZIMUtH
RESET KNOB 8
Figure 9. Panoramic telescope T149E1.
the aiming circle. When the executive announces"No. (so-and-so) is laid," the tube is oriented andshould not be traversed except on order of the exe-cutive.
40. Alines Aiming Posts, Assisted by No. 5
The piece having been laid as in paragraph 39,the executive may command AIMING POINT,AIMING POSTS, DEFLECTION 800, REFER.At this command the gunner sets 8 on the coarseazimuth scale and 0 on the micrometer scale and,with hand signals, directs No. 5 in the alinement ofthe aiming posts with the vertical line of the sightreticle. If, because of the nature of the terrain, theaiming posts cannot be set out at deflection 800, the
AGO 2790C 31
gunner turns the azimuth micrometer knob untilthe coarse azimuth and micrometer scales are onanother even-hundred-mil graduation. He alines theaiming posts at this new deflection. The chief ofsection reports the altered deflection to the exe-cutive "Sir, No. (so-and-so) 800 in canyon (or otherreason), laid on deflection 700." The executive willthen command NO. (SO-AND-SO) LAID, RESETCOUNTER TO 3200. The gunner resets azimuthcounter to 3200. All subsequent deflection changesmust be set on the azimuth counter. The tube isoriented and should not be traversed except on orderof the executive.
41. Lays Piece for Elevation(fig. 10)
The gunner sets the announced elevation on theelevation counter, then clamps the elevation countersetting knob in position with the clamping knob. Hethen elevates or depresses the tube in the directionindicated by the arrows in the elevation vernier untilthe indexes in the elevation vernier are alined. Finaladjustment will be made in the direction of increas-ing resistance.
42. Sets Common Deflection to Common Aiming Point AfterPiece Has Been Laid
The battery having been laid, the executive maycommand AIMING POINT, CHURCH STEEPLE,REFER. At this command, without moving thetube, each gunner turns his sight to the aimingpoint designated and reports the deflection to theexecutive. The executive then commands, COM-
32 AGO 2790C
' RIGHT
(®) WRONG
Figure 10. Alining elevation vernier indexes.
AGO 2790C 33
MON DEFLECTION 3200. At this command eachgunner pushes in on the azimuth counter reset knoband rotates it until 3200 is read on the scale of theazimuth counter. All subsequent deflection changesmust be set on azimuth counter. He makes a finalcheck to verify that the line of sight is still on theaiming point.
43. Sets or Changes Deflection
The command is DEFLECTION (SO MUCH).If, for example, the command is DEFLECTION3300, the gunner rotates the azimuth knob in theappropriate direction until 3300 is read on the azi-muth counter. The gunner then traverses the pieceuntil the vertical hair of the reticle is on the leftedge of the aiming posts or on a designated aimingpoint. Final motion for traversing is from left toright.
44. Signals and/or Calls "Ready"
After the piece has been loaded and laid both indirection and elevation and is ready to fire, the gun-ner will call and/or signal "Ready," by shouting orby raising his right arm, to signify that the pieceis ready to fire.
45. Refers Piece
The command from the executive is AIMINGPOINT THIS INSTRUMENT (OR OTHERPOINT), REFER. Without disturbing the layingof the piece, the gunner turns only the sight until,with bubbles level, the vertical cross hair of the
34 AGO 2790C
reticle is on the point designated. He then reportsthe deflection, as read from the coarse azimuth andthe micrometer scales, to the executive, "Sir, No.(so-and-so) deflection (so much)."
46. Makes Corrections for Aiming Post Displacement
For details of correcting for aiming post displace-ment, see paragraph 101.
Section IV. DUTIES OF CANNONEERS AND DRIVER
47. No. 1, List of Duties(Detailed description of duties, pars. 48-53.)
a. Opens the breech prior to firing the first round.b. Wipes the bore dry prior to firing the first
round, assisted by No. 2.c. Loads the piece.d. Fires the piece.e. Throws expended cartridge cases out the left
side of the turret.f. Closes the breech at the completion of firing.
48. Opens Breech Prior to Firing First Round
No. 1 grasps the breech operating handle with hisright hand and releases the breech operating handlecatch. He then pushes down on the handle until thebreechblock locks in position.
49. Wipes Bore Dry Prior to Firing First Round
Before firing the first round, No. 1, assisted byNo. 2, thoroughly dries the bore and chamber to in-sure that no oil or water is present.
AGO 2790C 35
50. Loads Piece
No. 1 grasps the round with his right hand at thebase of the cartridge case and his left hand in frontof the rotating band. He then faces the breech and,after an elevation has been announced, inserts theround in the breech and pushes it home with hisright fist and announces "Set." It is extremely im-portant that he use his fist, to guard against gettinghis fingers crushed by the closing breechblock. No. 1will be particularly careful to avoid striking the fuzeagainst any portion of the howitzer. A round to beloaded will be held well out of the path of the recoiluntil the tube is again in battery.
51. Fires Piece
At the command FIRE by the chief of section,No. 1 grasps the lanyard and pulls it to the rear, be-ing careful to stay out of the path of recoil.
52. Throws Expended Cartridge Cases Out Left Side ofTurret
After the piece has been fired, No. 1 recovers theexpended cartridge case and throws it out the ex-pended ammunition hatch located on the left side ofthe turret.
53. Closes Breech at Completion of Firing
After firing is completed or when directed by thechief of section, No. 1 closes the breech by trippingthe extractors with the base of an expended cart-ridge case or other appropriate materiel. The ex-tractors should never be tripped by hand because of
36 AGO 2790C
the possibility of the hand being crushed by theclosing breechblock.
54. No. 2, List of Duties(Detailed description of duties, pars. 55 and
56.)
a. Passes prepared rounds to No. 1.b. Inspects and insures that fuze setting is cor-
rect.
55. Passes Prepared Rounds to No. 1
No. 2 receives prepared rounds from No. 3 andpasses them to No. 1. He positions himself duringfiring on the door of the ammunition stowage com-partment. As he passes the round to No. 1, hechecks to make sure that there are no nicks or burrson the rotating band. He hands the round to No. 1in such a position that No. 1 may readily receive itas prescribed in paragraph 50.
56. Inspects and Insures That Fuze Setting Is Correct
No. 2 checks the prepared round as he passes it toinsure that the fuze setting commanded is actuallyset on the projectile.
57. No. 3, List of Duties(Detailed description of duties, pars. 58-61.)
a. Fuzes projectiles or changes fuze.
b. Sets the fuze setter M26 or M28.
c. Sets fuzes.
d. Passes prepared round to No. 2.
AGO 2790C 37
58. Fuzes Projectiles or Changes Fuze
No. 3 removes the fuze or closing plug from theprojectile; removes (or replaces) the supplementarycharge, if necessary; and screws in the designatedfuze. In assembling fuzes to, or removing fuzesfrom projectiles, only the authorized fuze wrenchshould be used. Variable time (VT) fuzes should bescrewed in by hand and tightened with fuze wrenchM18, using only manual force. Do not hammer onthe wrench or use an extension handle. On fuzes soequipped, No. 3 removes the safety pull wire fromthe fuze.
59. Sets Fuze Setter M26 or M28
No. 3 releases the time scale clamping screwmarked "T" and, grasping the handle, turns thebody until the index on the body is opposite the an-nounced time on the time scale. He then locks thetime scale clamping screw, being careful not to dis-turb the setting. For accuracy, he looks squarelyat the scales and indexes in the same manner eachtime.
60. Sets Fuzes
a. Selective Superquick and Delay Fuzes. Whenfuze quick is commanded, No. 3 will verify thesuperquick setting. (The slot on the setting sleeveshould be alined with the letters SQ.) When fuzedelay is commanded, No. 3 will turn the settingsleeve until the slot is alined with the word DELAY.
b. Combination Time and Superquick Fuzes. Thecombination time and superquick fuze may be set
38 AGO 2790C
for time action. After fuzing the projectile, No. 3removes the safety pull wire from the fuze. Forpercussion action, the command is FUZE QUICK.For time fuzes, No. 3 verifies that the S on the set-ting ring is alined with the index on the fixed ring;if not, he sets it at S.
c. Setting Time Fuzes.(1) Using fuze setter M26 or M28. After
making the announced setting on the fuzesetter M26 or M28, No. 3 carefully placesthe setter over the fuze and turns the set-ter in the direction of increasing readingsuntil the notch on the time ring of thefuze engages the stop on the setting ringof the fuze setter. He places the handle inthe most convenient position, pushes downon the fuze setter until the notch fully en-gages the stop, and continues to turn it inthe direction of increasing readings untilthe pawl in the adjusting ring assemblydrops into the notch of the fixed fuze ring.This action prevents further turning andindicates that the fuze is set. He thenlifts the fuze setter from the fuze andmakes a visual check to see if the fuze isproperly set. If the fuze is not properlyset, he sets the fuze to S by turning thesetter in the direction of increasing read-ings and then resets the fuze.
(2) Using fuze setter M14 or M27. Fuze set-ters M14 and M27 are wrench-type set-ters in which the time scale on the fuze
AGO 2790C 39
is used in setting the fuze. With M500-series fuzes, No. 3 engages the key of thefuze setter in the notch on the setting ringof the fuze and rotates the lower cap in thedirection of increasing readings until theannounced time setting is opposite the in-dex mark on the fuze.
d. VT Fuzes. The older type VT fuzes (M97)operate and function in such a manner as to requireno setting by personnel. The new type VT fuzes(M513-series) have a time setting ring and areset by using the fuze setter M28 in the same man-ner as the M54-series time fuzes are set by usingthe fuze setter M26. However, if the fuze setterM28 is not available, the wrench-type fuze setteris used to set the new type VT fuzes. VT fuzes ofcertain lots are issued with a wax coating on theplastic ogive. This wax coating is necessary for theproper functioning of the fuze and should not be re-moved. VT fuzes should be used as issued; that is,with the wax coating on the ogive, if so issued, orwithout a wax coating, if so issued.
61. Passes Prepared Round to No. 2
No. 3 positions himself on the ground as near aspossible to the rear of the turret. After No. 3 com-pletes the setting of the fuze, he passes the preparedround to No. 2.
62. No. 4, List of Duties
(Detailed description of duties, pars. 63-65.)
a. Prepares charges.
40 AGO 2790C
b. Replaces increments in the cartridge case be-fore rounds are replaced in the container.
c. Assists No. 5 and driver in replacing ammuni-tion in containers as directed by chief of section.
63. Prepares Charges
The fire command will include the designation ofthe charge. No. 4 verifies the number of incrementsand removes those increments numbered higherthan the charge designated. He then replaces theremaining increments in the cartridge case in theiroriginal numerical order. After No. 4 has preparedthe charge, he fits the projectile in the cartridgecase. Care is taken to prevent damage to the lip ofthe cartridge case.
64. Replaces Increments in Cartridge Case Before RoundsAre Replaced in Container
Under the personal supervision of the chief of sec-tion, No. 4 replaces increments in cartridge casesfor all ammunition prepared for firing, but not fired.He checks carefully to see that all seven incrementsare present, in the proper condition, assembled inthe proper numerical order, and of the proper lotnumber.
65. Assists No. 5 and Driver in Replacing Ammunition inContainers as Directed by Chief of Section
See paragraph 69 for details of replacing am-munition in containers.
AGO 2790C 41
66. No. 5, List of Duties(Detailed description of duties, pars. 67-70.)
a. Sets out aiming posts.b. Removes ammunition from containers.c. Replaces unused ammunition in containers.d. Assists No. 4 in preparing charges as directed
by the chief of section.
67. Sets Out Aiming Posts
No. 5 sets out the aiming posts as described inparagraph 100.
68. Removes Ammuniton from ContainersNo. 5 removes the taped end from the cartridge
case portion of the ammunition container and tiltsthe container so that the cartridge case can be takenby No. 4 or the driver when available. He then re-verses the ends of the container and repeats theprocess so that the projectile is received by No. 4 orthe driver when available.
69. Replaces Unused Ammunition in ContainersUnder the personal supervision of the chief of
section and assisted by No. 4 or the driver as avail-able, No. 5 replaces unused ammunition in contain-ers. He checks carefully to insure that the lot num-ber on the projectile and cartridge case correspondsto the lot number on the container. He insures thatthe ammunition is in good condition and complete.
70. Assists No. 4 in Preparing Charges as Directed byChief of Section
See paragraph 63 for details of preparingcharges.
42 AGO 2790C
71. Driver, List of Duties
(Detailed description of duties, pars. 72 and73.)
a. Moves the motor carriage if large deflectionshifts are necessary.
b. Assists No. 5 in handling ammunition and per-forms such other duties as directed by the chief ofsection.
72. Moves Motor Carriage if Large Deflection Shifts AreNecessary
At the direction of the chief of section, the drivershifts the motor carriage to permit a large deflectionshift to fall within the on-carriage traverse limits.
73. Assists No. 5 in Handling Ammunition
When No. 5 is unable to keep up with the am-munition requirements, the chief of section may di-rect the driver to assist in the handling of ammuni-tion. See paragraphs 68 and 69 for details ofhandling ammunition.
AGO 2790C 43
CHAPTER 6
FIRING BY DIRECT LAYING
Section 1. TECHNIQUE OF FIRE
74. General
a. Firing by direct laying is a technique that de-mands special training. The section must operateas an independent unit. Targets taken under fire bythe section in direct laying are usually capable of re-turning fire on the section at pointblank range;therefore, speed and accuracy are extremely im-portant in direct laying missions.
b. For additional information on firing by directlaying, see FM 6-140.
75. Preparation of Range Card
a. The chief of section is responsible for defensein his assigned sector and should be prepared to fireon targets in other sectors.
b. As soon as possible after occupation of posi-tion, the chief of section measures or estimates theranges to critical points in likely avenues of ap-proach for enemy tanks and vehicles. For quickreference, he prepares a range card (fig. 11) uponwhich he notes these ranges.
c. If there are no prominent terrain features,stakes may be driven into the ground at critical
44 AGO 2190C
. \TEE
0 0 s 9Ot OUSEBRIUSH 600
900N-. //ORCHARD
tt BARN
Figure 11. Range card for direct laying.
points for reference. As time permits, the rangecard should be improved by replacing estimatedranges with more accurate ranges obtained by fir-ing, pacing, taping, vehicular speedometer readings,map measurements, or survey.
76. Field of Fire
The sector of fire for the howitzer should, if pos-sible, be cleared of all obstructions that might en-danger battery personnel when the howitzer is firedor that might hinder observation. Care should betaken not to disclose the location of the position.
77. Priority of Targets
Targets for firing by direct laying usually consistof tanks, vehicles, and personnel threatening thebattery. Personnel will seldom present themselves
AGO 2790C 45
as a clearly defined target. Normally, attacking in-fantry, using all available cover, reveal themselvesonly fleetingly. Fire should be conducted on the areacontaining the attackers rather than on individuals.Tanks usually attack in groups and may be accom-panied by infantry. First priority is given to attackof targets within the assigned sector of the howitzerand second priority to targets in other sectors.Priority within the assigned zone is given to-
a. Tanks at short ranges, threatening to overrunthe position.
b. Hull down stationary tanks covering the ad-vance of other tanks.
78. Ammunition and Fuzes
a. General. For close-in fires, a variety of fuzesand shells are available. When high explosive shellsare used, charge 7 is habitually used for speed, easein adjustment, imparting forward motion to frag-ments, and more effective fuze action. The flattrajectory resulting from use of charge 7, coupledwith dug-in howitzers, may make extremely close-in fire impossible owing to projectiles skipping with-out detonating on impact. At ranges of 200 to 400yards, fuzes may fail to function on hard, flatground; however, preparation of sectors of fire willremedy this situation. The terrain may be preparedfor direct fire by placing mounds of sandbags, dirt,or logs in the sector of fire. When direct fire isplaced on these points as they are approached by anattacking force, the necessity for adjusting fire isreduced.
46 AGO 2790C
b. Ammunition. Ammunition may be high ex-plosive (HE), high explosive antitank (HEAT), orwhite phosphorus (WP). HEAT is designed for,and is highly effective in, antitank and antivehiclefires. HE is ideally suited for antipersonnel fire andis effective against vehicles and tanks. WP may beused to set immobile tanks and vehicles on fire, torestrict defiles, and to produce casualties. However,consideration must be given to the effect of the re-sulting smoke screen on the defense of the howitzerposition.
c. Fuzes. HEAT projectiles contain base detonat.ing fuzes. WP projectiles are fuzed with a super-quick-delay fuze. HE projectiles may be fuzed withsuperquick-delay or time fuzes.
(1) Fuze quick is the most desirable fuze touse with HE shell on close-in targets. It ishighly effective and, since no fuze settingis required, is much faster to use.
(2) The time required to set the fuze and toadjust the point of impact for maximumricochet effect makes fuze delay less desir-able than fuze quick for close-in targets.When fuze delay is used to gain ricocheteffect, the point of impact is adjusted from10 to 30 yards in front of the target. Ifless than 50 percent of the bursts arericochet, the fuze should be changed toquick.
(3) Fuze time is the least desirable fuze forclose-in targets. At short fuze settings,variations in timing action give wide range
AGO 2790C 47
dispersion of bursts. Hence, this fuzeshould be used only for ranges of morethan 1,000 yards. The areas covered effec-tively by air and ricochet bursts are sim-ilar.
79. Trajectories
Trajectory characteristics change with the typeof ammunition and the charge fired. The followingtrajectory characteristics govern the conduct of fireby direct laying:
a. Ranges from 0 to 400 Yards Using HEAT orRanges from 0 to 600 Yards Using HE, Charge 7.Within range limits of 0 to 400 yards using HEATor 0 to 600 yards using HE, charge 7, the trajectorywill be flat enough to prevent an 8-foot high tankfrom passing safely under it. If fields of fire andterrain allow, the upper range limits for the am-munition and charge used are the ideal at which toopen fire by direct laying. Direct fire can then beconducted over the maximum time without missesif deflection is correct. Also, there is less risk ofobscuring the target with the smoke from a shortburst.
b. Ranges from 400 to 700 Yards Using HEATor Ranges from 600 to 1,000 Yards Using HE,Charge 7. Range limits of 400 to 700 yards usingHEAT or 600 to 1,000 yards using HE, charge 7include the zone in which the trajectory is suffi-ciently flat to permit direct estimation of rangewithout actually bracketing the target. Assuminglittle dispersion, if a hit is obtained at the bottom of
48 AGO 2790C
an 8-foot high tank firing at the upper range limit,700 yards, for example, with HEAT, a 100-yardrange increase will result in a round that will justbrush the top of the tank. During adjustment withinthis zone, range changes should seldom be more than100 yards, and frequently range changes of 50 yardswill be sufficient. The upper limits mentioned hereinare the greatest ranges at which direct fire shouldbe opened unless tactical conditions require other-wise. A trained crew should obtain a hit by thesecond shot.
c. Ranges from 700 to 1,300 Yards Using HEATor Ranges from 1,000 to 1,800 Yards Using HE,Charge 7. The zone of 700 to 1,300 yards usingHEAT or 1,000 to 1,800 yards using HE, charge 7includes the ranges at which hits by direct fire areonly reasonably possible. Bracket methods are nor-mally used to obtain adjustment in this zone. Thereis more dispersion in this zone, and direct fire shouldnot be opened at these ranges unless surprise is notimportant.
d. Ranges Over 1,300 Yards Using HEAT orRanges Over 1,800 Yards Using HE, Charge 7. Atranges over 1,300 yards using HEAT or over 1,800yards using HE, charge 7, firing by direct laying isnot advisable against moving targets. Dispersion isthe controlling factor. Ranges must be known ac-curately or determined by bracketing. At theseranges the slope of fall of the projectile becomes sogreat that a hit on a moving target is very difficultto obtain.
AGO 2790C 49
80. Vertical Displacement Table
Vertical displacement is the change in the pointof burst (up or down) between two rounds firedwith different range settings at an upright target.Table IV shows the vertical displacement for a100-yard range change at various ranges, firingshell HEAT and shell HE, charge 7. The use ofvertical displacement in direct fire is explained inFM 6-140.
50 AGO 2790C
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81. Direct Laying, Using Telescope T150E1
The telescope T150E1 is normally the only sight-ing instrument used for direct laying. Paragraphs83 through 97 apply to use of the telescope T150E1only. The reticle pattern of the telescope is correctwhen using shell, HEAT. The cross in the patternrepresents zero range and deflection for boresight-ing the broken vertical line in the vertical center ofthe reticle. The broken lines below the cross repre-sent 400-, 800-, 1,200-, 1,600-, 2,000-, and 2,400-yard ranges. Each horizontal line in the reticlerepresents a deflection of 5 mils. A cant correctionknob and leveling vial are provided on the elbowsection of the telescope which permits correctionfor up to 15 ° of cant.
82. Direct Laying, Using Panoramic Telescope T149E1
The panoramic telescope T149E1 is used for di-rect laying in case of emergency only. Direct layingwith the panoramic telescope T149E1 is muchslower and less accurate than with the telescopeT150E1. For a detailed discussion of the use of thepanoramic telescope T149E1 in direct laying, seeTM 9-717A.
Section II. DUTIES OF CHIEF OF SECTION
83. List of Duties(Detailed description of duties, pars. 84-91.)
a. Conducts the fire of his howitzer.b. Alerts his section.c. Identifies or selects the target.
AGO 27900 53
d. Selects the charge, fuze, and projectile.
e. Determines the direction of movement of thetarget.
f. Determines the lead in mils.
g. Gives the command for range.
h. Gives subsequent commands based on observedeffect.
84. Conducts Fire of His HowitzerThe chief of section conducts the fire of his how-
itzer when the executive officer commands TARGET(IDENTIFICATION), FIRE AT WILL, or simplyFIRE AT WILL.
85. Alerts His SectionThe command to alert the section is 1. CANNON-
EERS, 2. POSTS. At the command, members ofthe section move to their posts to be ready for theinitial fire command. If the target is outside themaximum traverse of the howitzer, the alert is fol-lowed by the necessary signals to the driver to getthe carriage pointed in the approximate directionof the target.
86. Identifies or Selects TargetIf the executive officer designates an object as the
target, the chief of section must identify the targetcorrectly. If the target is a group of tanks or otherobjects, the chief of section selects the target whichis the greatest threat to his own position or theposition of the supported troops. He repeats theidentification to his section, using the minimum
54 AGO 2790C
number of words, such as TANK or INFANTRY(OR OTHER TARGET).
87. Selects Charge, Fuze, and Projectile
The chief of section commands the appropriateitems in sequence, such as SHELL HE, CHARGE 7,FUZE ____, or SHELL HEAT. He selects thecharge, fuze, and projectile in accordance with para-graph 78.
88. Determines Direction of Movement of Target
The chief of section determines the direction ofmovement of the target and commands TRAVERSERIGHT (LEFT), STEADY-ON. While givingthese commands he looks along the tube or throughthe periscope M15A1.
89. Determines Lead in Mils
The amount of lead in mils for moving targets isdetermined by considering the speed of the target,the range, the course, and the ammunition beingfired. Figure 12 shows approximate initial leadsthat should be used for various target speeds andcourses in firing HEAT and HE, charge 7. Theinitial command for lead is LEAD (SO MUCH).During adjustment the lead is changed by the com-mand RIGHT (LEFT) (SO MUCH).
90. Gives Command for Range
The command is RANGE (SO MUCH). Therange commanded by the chief of section is thatrange to be set on the sight reticle. During the ad-
AGO 2790C 55
LEAD (MILS)SPEED Target traveling perpen- Target traveling 45 °
dicular to line of fire to line of fire
HEAT Charge 7 HEAT Charge 7
Slow (0-1OMPH) 5 5 5 5Medium (10-20 MPH) 20 15 1 5 10Fast (aover 20 MPH) 30 25 20 20
Figure 12. Approximate leads.
justment of fire, range is corrected by the commandADD (DROP) (SO MUCH).
91. Gives Subsequent Commands Based on ObservedEffect
The chief of section observes each round andgives the necessary commands for changes in leadand range to adjust the burst to the target.
Section III. DUTIES OF REMAINDER OF SECTION
92. Gunner, List of Duties
(Detailed description of certain duties, pars.93-95.)
a. Corrects for cant of the howitzer.b. Lays on the target with the announced lead
and range.c. Tracks the target.d. Commands FIRE.e. Follows subsequent commands.
93. Corrects for Cant of Howitzer
The gunner checks the leveling vial on the elbowsection of the telescope and rotates the cant cor-
'56 AGO 27900
rector knob until the bubble is centered. This opera-tion corrects for up to 150 of cant.
94. Lays on Target with Announced Lead and Range andTracks Target
The lead and range are measured on the horizon-tal reticle scale of the telescope. The cross in thereticle pattern represents zero range and deflection.The horizontal lines below the cross represent 400-,800-, 1,200-, 1,600-, 2,000-, and 2,400-yard ranges.Each segment and space represents 5 mils of de-flection. The gunner then tracks the target by usingthe traverse and elevating handwheels, keeping theproper sight picture on the center of the target.See figure 13 for proper sight picture.
95. Commands Fire
After No. 1 has called "Set," the gunner com-mands FIRE, when ready.
96. No. 1
The duties of No. 1 during direct fire are to openthe breech on the first round, to load the howitzer,to call "Set" when the howitzer is loaded, and tofire the howitzer at the gunner's command FIRE.
97. Remainder of Section
The remaining cannoneers perform their dutiesas prescribed for firing by indirect laying.
AGO 2790C 57
10-- M
- - I- --16 - - I - - 16
24 - - i - - 24
7633305
Figure 1S. Gunner's sight picture, telescope T150EI,shell HEAT (lead 15 mils, range 800 yards).
58 AGO 2790C
CHAPTER 7
TECHNIQUES AND SITUATIONS THATREQUIRE ATTENTION
98. Precision in Laying
a. Sighting and laying instruments, fuze setters,and elevating and traversing mechanisms must beproperly operated to reduce the effects of lost mo-tion. For uniformity and accuracy, the last motionin setting instruments and in laying should be in thedirection prescribed in this manual. To insure ac-curate laying, personnel who lay the howitzer mustbe required to verify the laying after the breechhas been closed.
b. The line of sight when setting and reading ascale or centering a bubble must be at a right angleto the scale or level vial to prevent parallax errors.Bubbles must be centered exactly.
c. For uniformity and accuracy in laying on aim-ing posts, the vertical cross hair in the reticle of thepanoramic telescope must be alined with the leftedges of the aiming posts.
99. Aiming Points
a. General. After the howitzer has been laid ini-tially for direction, it is referred to the aiming postsand usually to one or more distant aiming points.An aiming point must have a sharply defined point
AGO 2790C 59
or vertical line which is clearly visible from thehowitzer so that the vertical cross hair of the pano-ramic telescope can be alined on exactly the sameplace each time the howitzer is relaid.
b. Distant Aiming Point. A distant aiming pointis one at sufficient distance (at least 2,000 yards)so that normal displacements of the howitzer infiring or traverse will not cause a horizontal angularchange in direction (with the same settings on theazimuth scales) of more than one-half mil. Theexecutive officer usually designates the distant aim-ing point or points to be used.
100. Aiming Posts
a. Two aiming posts are used for each howitzer.Each aiming post is equipped with a light for useat night. The most desirable distance from thehowitzer to the far aiming post is 100 yards, con-sidering accuracy of laying, visibility, and ability tocontrol the aiming post lights. First, the far aimingpost is set up and alined. The near aiming post isthen set up and alined halfway between the faraiming post and the howitzer. The vertical crosshair of the panoramic telescope must be on the leftedge of the aiming posts for proper alinement. Toinsure equal spacing of aiming posts, the distanceto both the near and the far aiming post shouldbe paced by the same man. If ground conditionsmake pacing inaccurate, the distance from the how-itzer to the aiming posts may be measured by usingthe panoramic telescope and the aiming post asmeasuring devices (d below).
60 AGO 2790C
b. For night use, the aiming post lights shouldbe adjusted so that the far light will appear severalfeet above the near light. On flat terrain this maybe accomplished by using only the lower half of thenear aiming post. The two lights placed in this waywill establish a vertical line for laying the howitzer.
c. Since the panoramic telescope is mounted atconsiderable distance from the center of rotation ofthe top carriage, large changes in deflection willcause misalinement of the aiming posts.
d. To measure the distance from howitzer to aim-ing posts, the stadia method may be employed byusing the panoramic telescope and the aiming postas measuring devices. No. 5 cannoneer, in settingout the aiming posts, holds the upper section of oneof the aiming posts in a horizontal position, perpen-dicular to the line of sighting. The gunner measuresthe length of this section in mils on the horizontalcross hair of the panoramic telescope. For example,the upper section of the aiming post is 41/2 feet longand measures 15 mils when it is 100 yards from thehowitzer. The proper location for the near aimingpost, in this case, would be at the point at whichthe 41/2-foot section measures 30 mils. In manycases, the ideal spacing of 50 and 100 yards cannotbe obtained, but the aiming posts will be properlyspaced when the near aiming post is set at a pointwhere one section of the aiming post (41/2 ft) heldhorizontally measures twice the number of mils onthe horizontal cross hair that it measured at thefar aiming post location. This measurement may beperformed at night by attaching the night lighting
AGO 2790C 61
devices on the ends of one section of an aiming postand holding it horizontally.
101. Correction for Displacement of Aiming Posts
When the gunner notes that the vertical crosshair of the panoramic telescope is displaced fromthe line formed by the two aiming posts (or aimingpost lights), he lays the howitzer so that the faraiming post (light) appears exactly midway be-tween the near aiming post (light) and the verticalcross hair (fig. 14). If the displacement is due totraversing the howitzer, the gunner continues to layas described above. If the displacement is due toprogressive shifting of the carriage from shock offiring or other cause, the gunner will notify the chiefof section, who, at the first lull in firing, will notifythe executive and request permission to realine theaiming posts. To realine, the howitzer is laid withthe far aiming post midway between the near aim-ing post and the vertical cross hair (fig. 14). Thefar aiming post is moved into alinement with thevertical cross hair of the telescope and then the nearaiming post is alined. If terrain conditions make itimpossible to move 1 of the 2 aiming posts, thehowitzer is laid for direction and both aiming postsare alined to the right rear of the howitzer at thecommanded deflection.
102. Testing Target
a. If the regular testing target or a visible dis-tant aiming point is not available, a testing targetmay be improvised either by drafting the aiming
62 AGO 2790C
FAR AIMING POST FAR AIMING POST
NEAR AIMING POST PT
LEFT RIGHTDISPLACEMENT DISPLACEMENT
Figure 14. Gunner's sight picture of aiming posts in properrelationship when correcting for displacement.
diagrams to the correct measurements (TM 9-324A) or by the following technique:
(1) Carefully boresight the howitzer on a dis-tant aiming point.
(2) Place a flat piece of masonite, wallboard,or similar material covered with a sheetof weather-resistant paper 50 yards infront of the howitzer so that its face isperpendicular to the line of sight throughthe tube. To render the testing targetstable, the target may be fastened to astand constructed for that purpose.
(3) Without disturbing the relationship of thetelescopes to the tube, mark on the paperthe centers of the lines of sight throughthe telescopes and the tube.
AGO 2790C 63
(4) From the centers marked, construct aim-ing diagrams such as those found on stand-ard testing targets.
b. For use in either leveling or canting the test-ing target, a mil scale may be drawn at the bottom ofthe target. A small nail at the top marks the centerfrom which the arc was drawn and provides a hookfrom which to suspend the plumb line (fig. 15).
c. Vertical reference lines may be drawn throughthe centers of each of the diagrams (fig. 15). Theselines may be used when the trunnions cannot beleveled by setting the testing target with the cantangle of the howitzer. The target is tilted until theline of sight through the tube tracks the tube refer-ence line when the tube is elevated or depressed.Then, the panoramic telescope should be adjustedso that its vertical cross hair tracks between theappropriate reference lines when the tube is elevatedor depressed.
103. Cease Firing
The command CEASE FIRING is normally givento the howitzer section by the chief of section, butin emergencies anyone present may give the com-mand. At this command, regardless of its source,firing will cease immediately. If the howitzer isloaded, the chief of section will report that fact tothe executive. The executive acknowledges this an-nouncement by saying "No. (so-and-so) loaded."If CEASE FIRING came from the fire directioncenter, firing is resumed at the announcement of theelevation. If CEASE FIRING came from within
64 AGO 2790C
PANORAMIC TELESCOPE- / IIT149E1
43-43/64 IN-20 IN -
TELESCOPET150EI
4 IN
105-MM HOWITZER-_T96E1
8-3/4 IN
MIL SCALE(Not to Scole)
Figure 15. Vertical reference lines and mil scaledrawn on testing target.
AGO 27900 6
the firing battery, the executive will investigate thecondition that caused the command to be given.When the condition is corrected, firing is resumedat the executive's announcement of the elevation.
104. Changes in Data During Firing
a. If a change in firing data is made before thehowitzer is loaded, the corrected data is announced.The new data is then set off and firing is resumedat the announcement of the elevation.
b. If a change in firing data is made after thehowitzer is loaded, the command CEASE FIRINGis given. If no change in fuze setting is required,or if the howitzer is loaded with percussion-fuzedshell, the new data is set off and firing is resumedat the announcement of the elevation. If the how-itzer is loaded with time-fuzed shell and the datarequires a change in fuze setting, the chief of sectionwill suspend firing and that fact will be reported tothe executive; for example, "No. 2 loaded, time (somuch)." The howitzer will not be unloaded unlessdirected by the executive. In continuous fire,changes in data are so applied as not to stop the fireor break its continuity.
105. To Unload Piece
a. A complete round, once loaded, should alwaysbe fired in preference to being unloaded, but militarynecessity may dictate otherwise.
b. When the command UNLOAD is given, No. 1opens the breech slowly; No. 2, standing at thebreech, receives the ejected round or cartridge case.
06 AGO 2790C
c. Should the extractor fail to extract the com-plete round, the staff and unloading rammer (head)is used. Unloading will be done only under the im-mediate supervision of an officer. The officer in-spects the recess in the head of the rammer toassure that it is free from obstructions. No. 1 theninserts the rammer in the bore until the head in-closes the fuze and comes into contact with theprojectile. He pushes and, if necessary, taps therammer staff slightly or operates the spring-oper-ated rammer until the round is dislodged. He thenpushes the round out of the breech and No. 2 re-ceives it.
d. If the cartridge case is extracted but not theprojectile, No. 1 fills the chamber with waste andcloses the breechblock. He dislodges the projectileas in c above. No. 2 then opens the breech, removesthe waste, and receives the projectile as No. 1pushes it to the rear.
e. For further information on unloading, see FM6-140 and TM 9-324A.
f. In case of a misfire, the instruction in para-graph 142 will be followed.
106. Care of Ammunition
a. To insure uniform results in firing, to prolongthe life of the tube, and to avoid accidents, caremust be exercised in the storage and handling ofammunition at the battery. Provisions of TM 9-1900 applicable to field service should be followedcarefully. In the field, conditions existing in each
AGO 2790C 67
position will determine the amount of time, labor,and materials required to store and preserve theammunition adequately. If the position is to beoccupied for only a few hours, a tarpaulin spreadon the ground may be sufficient; for longer periodsof time, more elaborate facilities should be provided.
b. Ammunition must be protected from damage.When ammunition is received, it should be sortedinto lots and placed in the best available storage.Powder temperature should be kept as uniform aspossible. Ammunition data cards should be keptuntil after all ammunition for that lot is expended.Ammunition should be left in containers until itsearly use is expected. Protection should be providedagainst moisture, dirt, direct rays of sun and, as faras practicable, artillery fire and bombing. Protec-tion from weather, dirt, and sun may be obtainedby the use of tarpaulins below and above ammuni-tion and dunnage between the layers. Projectilesstacked in the open should be raised off the groundby at least 6 inches. If drainage is not good, ditchesshould be dug around the stacks. A liberal use ofdunnage should be made between layers, and cover-ing tarpaulins should be raised at least 6 inchesfrom the stack to insure adequate ventilation. Eachstack should contain not more than 75 rounds andshould be not more than 4 layers high. Stacks shouldbe at least 10 yards apart.
c. For further information on care of ammuni-tion, see FM 6-140, TM 9-324A, TM 9-1900, andTM 9-1901.
68 AGO 2790C
107. Section Data Board
When positions are occupied for more than a fewhours, data boards may be used by each section forrecording such items as deflections to aiming points,calibration corrections when appropriate, minimumelevations, data for barrages and counterprepara-tions, and other data which may be needed quickly.If such information assumes a standard pattern,the section may paint a form on the inside of thehull and chalk in the various items of informationin the appropriate spaces.
108. Hand Signals
Standard hand signals are used to indicate to thedriver the proper movement of the motor carriage.Dismounted signals are given facing the driver andare as illustrated in FM 21-60 and FM 25-10.
AGO 2790C 69
CHAPTER 8
BORESIGHTING AND BASIC PERIODIC TESTS
Section I. GENERAL109. Purpose and Scope
The purpose of this chapter is to outline the pro-cedures for boresighting and for making basic peri-odic tests of on-carriage fire control equipment. Theprocedures covered will include only those that maybe accomplished at battery level.
110. Equipment
The equipment listed in a through d below isneeded for performing boresighting and periodictests.
a. Boresights. Front and rear boresights or im-provised substitutes are necessary for boresightingand testing. If boresights are not available, crosshairs may be fastened on the muzzle and the firingpin hole in the breechblock bushing may be used asa rear sighting guide by removing the firing lockfrom the closed breechblock.
b. Testing Target. A testing target (par. 102) orsuitable substitute is needed for both boresightingand testing. If the testing target is not available,a clearly defined aiming point 2,000 yards or morefrom the gun may be used for boresighting.
70 AGO 2790C
c. Tools. The section equipment includes all thenecessary tools for boresighting and testing. Caremust be taken in using the screwdrivers andwrenches to insure that damage to fastenings doesnot result through carelessness or the use of inap-propriate tools.
d. Plumb Line. Although not essential for bore-sighting, it is necessary that a plumb line be usedin the basic periodic test in order to obtain maxi-mum accuracy. The farther from the gun that theplumb line is placed, the longer the line must be.To keep a long plumb line taut it may be necessaryto add weight to the line. Wrenches or rocks maybe used. The tendency of the weight to swing maybe decreased by placing a bucket containing wateror other liquid under the plumb line so that theplumb bob is partially immersed in the liquid. Aplumb line strung from a building or tree is desir-able and should be used if possible. Units in gar-rison may find it convenient to rig a plumb line ona building. The line may then be nailed in placeso that it can be used permanently.
Section II. BORESIGHTING
111. General
a. Description. Boresighting consists of aliningthe line of sight through on-carriage fire controlinstruments parallel to the line of sight through thecenter of the tube. Boresighting is conducted bysection personnel before firing and during lulls infiring.
AGO 2790C 71
b. Methods. The three general methods of bore-sighting the weapon are the-
(1) Testing target method.(2) Distant aiming point method.(3) Standard angle method.
c. Leveling. Prior to starting the tests, the how-itzer should be placed in the center of traverse. Thevehicle should be placed upon ground as level aspossible, since no means are provided on the car-riage for cross-leveling the trunnions. The groundmay be built up under one track to assist in approxi-mately leveling the trunnions. There should be nomore than 20 mils of cant in the trunnions duringany boresighting operation.
112. Conditions
The on-carriage sighting equipment of the weaponis in correct adjustment and "boresighted" whenthe conditions in a through d below exist.
a. Mounts and instruments are securely attachedand there is no binding or excessive backlash be-tween the gears.
b. The lines of sight of on-carriage sightingequipment are parallel to the axis of the bore.
c. All scales and indexes read zero.
d. All bubbles are leveled.
113. Testing Target Methoda. General. It is essential that the proper testing
target be used for the weapon being boresighted.If a testing target is not available, a substitute may
72 AGO 2790C
be constructed as explained in paragraph 102. Thetesting target method consists of boresighting byusing the aiming diagrams on the testing target asaiming points. The steps to be followed are as fol-lows:
(1) Trunnions. Although it is not absolutelynecessary to level the trunnions for bore-sighting, it is advisable to do so wheneverpossible. Accurate results can be obtainedmore readily if the trunnions are level,because then a corresponding tilt does nothave to be introduced in the mounts andtesting target. In no case should there bemore than 20 mils cant.
(2) Tube. Level the tube by using the gunner'squadrant on the leveling plates of thebreech ring. Make certain that the shoeson the gunner's quadrant are positionedbetween the engraved lines on the levelingplates.
(3) Boresights. Open the breech and insertthe breech boresight in the chamber. At-tach the muzzle boresight, stretching linencords across witness marks on the muzzleand securing the ends by placing a straparound the end of the muzzle over thecords.
(4) Panoramic telescope mount level. The levelof the locating plate is checked by insuringthat the bubbles in the leveling segmentlevel vials and the leveling mechanism levelvials are accurately centered.
AGO 2790C 73
b. Elevation Counter. To make the elevationcounter reading agree with the tube elevation, placethe gunner's quadrant on the breech pads and, byelevating or depressing, bring the tube to 0 eleva-tion. Rotate the elevation counter setting knob untilthe elevation vernier indexes are alined. If thecounter reading does not agree with the gunner'squadrant reading within plus or minus one-half mil,zero the elevation counter, loosen the lock setscrewin the side of the bellcrank (fig. 16) and, with a% 2-inch hex setscrew wrench, turn the bellcrankadjusting screw until the elevation vernier indexesare alined. Tighten the lock setscrew while makingcertain that the adjustment does not change.
Note. Some T179 mounts will have a setscrew or cap-screw on top of the bellcrank adjusting screw. This screwmust be removed before the bellcrank adjustment can bemade.
c. Testing Target Alinement. Place the testingtarget at least 50 yards in front of the howitzerwith the face of the target perpendicular to the lineof sight through the tube. Position the target sothat the bore diagram is alined with the boresight.While elevating and depressing the tube, tilt thetarget until the intersection of the muzzle boresightcords tracks between the vertical reference lines onthe bore diagram without deviation. Fix the targetin this position. Elevate or depress the tube to alinethe intersection of the muzzle boresight cords withthe center of the bore diagram.
d. Panoramic Telescope Alinement. Rotate theelevation and azimuth knob until the horizontal and
74 AGO 2790C
E f
Figure 16. Bellerank adjustment.
vertical lines of the reticle pattern are alined withthe horizontal and vertical lines respectively on thepanoramic telescope diagram on the testing target.The coarse azimuth scale and the micrometer scaleof the panoramic telescope should now read 0; ifthey do not, loosen the locking screws on themicrometer scale and slip the micrometer scale to 0.Then tighten the locking screws, being careful notto disturb the setting of the telescope or scales.
e. Direct Fire Telescope Alinement. After pro-cedures prescribed in c above are performed, rotatethe cant correction knob to level the cant correction
AGO 2790C 75
level vial. Unlock the boresight knob locking levers.Rotate the azimuth and elevation boresight knobsuntil the cross hairs at zero range on the reticlepattern are alined with the center of the direct firetelescope diagram on the testing target. If thecross hairs of the telescope cannot be brought intocoincidence with the lines on the aiming diagram byusing the boresight knobs, notify ordnance main-tenance personnel.
114. Distant Aiming Point MethodThe distant aiming point method of boresighting
consists of alining the lines of sight of on-carriagefire control equipment and the line of sight throughthe axis of the tube on a common point at least2,000 yards away from the howitzer. A distant aim-ing point may be used if a testing target is notavailable or if its use is impractical. The stepsprescribed for the testing target method apply ex-cept that both the boresights and the optical sightsare alined on the same point instead of on separatediagrams of a testing target. Accurate leveling ofthe trunnions is unnecessary.
115. Standard Angle Method
a. General. Conditions may exist when the bore-sighting methods previously described are imprac-tical. Under such circumstances, the howitzer maybe boresighted by referring to a selected point onthe muzzle. The deflection and elevation anglesnecessary to refer the line of sight of the panoramictelescope to the selected point on the muzzle arereferred to as the standard angles. Once the stand-
76 AGO 2790C
ard horizontal and vertical angles are determined,they may be used for quick boresighting when moreprecise methods cannot be used. Correction of mis-alinement as a result of this test should be verifiedby a more accurate method at the earliest oppor-tunity. In using the standard angle method of bore-sighting, be sure that the position of the recoilingparts with respect to the nonrecoiling parts is thesame as when the standard angles are determined.
b. Preliminary Operations. The ideal time to de-termine the standard angles for later use is afterperforming basic periodic tests when the trunnionsare level (par. 111c) and the panoramic telescopemount is known to be in correct alinement (par.113d). The procedure for determining standardangles is as outlined in (1) through (8) below.
(1) With the tube in battery, scribe lines inthe paint to mark the normal position ofthe parts that move in recoil with respectto the parts which do not move in recoil.
(2) Boresight the howitzer by using a testingtarget.
(3) With adhesive tape, fasten a bright com-mon pin in the right horizontal witnessmark at the muzzle of the tube. Allowthe pin to project to the right of themuzzle (fig. 17).
(4) Fasten the telescope parallax shield in placeover the eyepiece.
(5) By turning the azimuth micrometer scaleand elevating or depressing the tube as
AGO 2790C 77
50 50
111 l Il 11111 I lllllllllllII
PIN
Figure 17. Sight picture of projecting pin.
78 AGO 270DC
necessary, place the horizontal cross hairsof the panoramic sight on the metal pinin the right horizontal witness mark ofthe tube.
(6) Verify that the sight mount is level andthat the intersection of the horizontal andvertical cross hairs of the panoramic tele-scope are exactly on the junction of thepin with the muzzle.
(7) Read and record the deflection from thepanoramic telescope, estimating to thenearest one-fourth mil. This is the stand-ard azimuth angle for the howitzer tested.
(8) With the gunner's quadrant seated on thequadrant seats, measure and record theelevation of the tube to the nearest one-fourth mil. This is the standard elevationangle for the howitzer tested.
c. Performance of Standard Angle Method. Oncethe standard angles have been determined and re-corded, the steps in performing the standard anglemethod of boresighting are as outlined in (1)through (5) below.
(1) Verify that the parts that move in recoilare in the same position with respect tothe nonrecoiling parts as they were whenthe standard angles were determined.
(2) Fasten a pin in the right horizontal wit-ness mark of the muzzle so that the pinprojects out to the right of the muzzle.
(3) Place the parallax shield on the eyepiece ofthe telescope.
AGO 2790C 79
(4) Set off the standard elevation and azimuthangles (b(6) and (8) above).
(5) If the intersection of the cross hairs of thepanoramic telescope is not exactly on thejunction of the pin and the muzzle, thesight is out of adjustment. If the azimuthangle is in error, it may be corrected bybattery personnel by slipping the azimuthmicrometer scale. If the elevation angleis in error by more than one-half mil,bellcrank adjustment (par. 113b) must beperformed.
Section III. BASIC PERIODIC TESTS
116. General
Basic periodic tests are performed by the sectionunder the supervision of the battery executive andthe artillery mechanic. These tests are performedat the discretion of the unit commander. Suggestedtimes for performance of the tests are once eachyear if the howitzer is used only for nonfiring train-ing; once every 3 months if the howitzer is fired;as soon as possible after intensive use, accidents,or traversing extremely rough terrain; and when-ever the howitzer fires inaccurately for no readilyapparent reason. The tests reveal whether or notthe on-carriage sighting equipment, the gunner'squadrant, and the fuze setter are in correct adjust-ment. Preparation for the tests includes-
a. Boresighting the howitzer.
so80 AGO 2790C
b. Placing the motor carriage on a site that isas near level as possible.
c. Preparing parallax shields for the panoramictelescope T149E1 and telescope T150E1 for it willbe necessary to eliminate parallax in viewing aplumb line or testing target at close range. Theshield should be the same diameter as the eyepiecelens housing. The shield should be made of stiffcardboard or brass shim stock and should have avertical and horizontal centered slot l/16-inch wideby 1/4 -inch long. The shield should be placed infront of the eyepiece with the slot in the verticalposition.
d. Establishing a suitable plumb line for thetests (par. 110d).
117. Test of Cross-Level Setting, Telescope Mount T179
For test of cross-level setting, telescope mountT179, see TM 9-324A.
118. Test of Longitudinal-Level Setting, Telescope MountT179
For test of longitudinal-level setting, telescopemount T179, see TM 9-324A.
119. Test of Elevation Counter Synchronization
With the gunner's quadrant placed on the breechpads, take elevation readings at 0, 225, 625, 1,025,and 1,155 mils, and if the elevation counter andthe gunner's quadrant do not agree within 1/2 milat 0 elevation and 1 mil at each of the other read-ings, the synchronization adjustment must be madeby qualified ordnance maintenance personnel.
AGO 2790C 81
120. Test of Plumb of Reticles in Telescopes T149E1 andT150E1
For test of plumb reticles T149E1 and T150E1,see paragraph 87c(6), TM 9-324A.
121. Test of Gunner's Quadrant
The gunner's quadrant must be in proper adjust-ment before conducting tests and adjustments ofother sighting and fire control equipment. Inspectthe shoes of the gunner's quadrant for dirt, nicks,or burs. Similarly, inspect the leveling plates on theupper surface of the breech ring. Dirt, nicks, or burson these surfaces will cause the instrument to give in-accurate readings. For detailed testing of the gun-ner's quadrant, see paragraphs 122 through 124.
122. End-For-End Test, Gunner's Quadrant
a. Set both the index arm and the micrometerscale of the gunner's quadrant at zero, making surethat the auxiliary indexes match.
b. Place the quadrant on the leveling plates ofthe breech ring with the "line of fire" arrow on thequadrant pointing toward the muzzle and centerthe quadrant bubble by turning the elevating hand-wheel.
c. Reverse the quadrant on the leveling plates(turn it end-for-end). If the bubble recenters, thequadrant is in adjustment and the test is completed.
d. If the bubble does not recenter, try to center itby turning the micrometer knob. If the bubble cen-ters, read the black figures on the micrometer scale
82 AGO 2790C
and divide by 2. This result is the correction. Setthis correction on the micrometer and level the tubeby using the elevation handwheel. Check again byturning the quadrant end-for-end. The bubble
~should recenter when the quadrant is reversed. Ifthe correction of error is more than plus or minus0.4 mil, the quadrant must be adjusted by ordnancemaintenance personnel.
e. If the bubble does not center as in d above,move the radial arm down 1 graduation (10 mils)and perform the following operations: Turn themicrometer until the bubble centers; take the read-ing on the micrometer, add 10 to it, and divide thesum by 2; place this result on the micrometer, leav-ing the radial arm at minus 10; center the bubblewith the elevation handwheel; and check by turningquadrant end-for-end. The bubble should recenter.If the correction of error is more than plus or minus0.4 mil, the quadrant must be adjusted by ordnancemaintenance personnel.
123. Micrometer Test, Gunner's Quadrant
a. Set the radial arm to read 10 mils on the ele-vation scale, and set the micrometer at 0.
b. Place the quadrant on the leveling plates onthe breech ring with the "line of fire" arrow point-ing toward the muzzle, and center the quadrantbubble by elevating the tube.
c. Set the radial arm at 0 on the elevation scale,and set the micrometer at 10 mils.
AGO 21790 83
d. Without disturbing the laying of the tube, re-seat the quadrant on the leveling plates. The bubbleshould center.
e. If the bubble does not center, the micrometeris in error and must be adjusted by ordnance main-tenance personnel.
124. Comparison Test, Gunner's Quadrant
Compare readings taken at low, medium, andhigh elevations with all of the gunner's quadrantsof a battery on the leveling plates of a single piece.The trunnions of this piece should be level. Anyquadrant differing from the average by more than0.4 mil at any elevation should be sent to ordnancemaintenance personnel for adjustment.
125. Application of Correcton, Gunner's Quadrant
When a gunner's quadrant requires a correctionas determined by the end-for-end test, the correctionis not applied during firing. The correction is re-corded and applied only when tests are made.
126. Test of Fuze Setters
Examine the stop which fits into the slot in themovable time ring and the adjusting pawl whichengages the notch in the fixed fuze ring to see thattheir edges are not burred or bent. Depress the ad-justable pawl against its spring to see that themovement of the pawl is free. Test the fuze setterwith fuzes for which it is designed; the time scaleon the fuze setter must have the same graduationsas the time ring on the fuze.
84 AGO 2790C
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CHAPTER 9
MAINTENANCE AND INSPECTIONS
127. General
Maintenance and inspection are essential to in-sure that the section is prepared to carry out itsmission immediately. Systematic maintenance andinspection drills provide the best insurance againstunexpected breakdown at the critical moment whenmaximum performance is essential.
128. Disassembly, Adjustment, and Assembly
Disassemblies and adjustments of the weaponauthorized to be performed by battery personnelare prescribed in TM 9-717A and TM 9-324A,supplemented by instructions in Department of theArmy supply manuals. No deviations from theseprocedures is permitted unless authorized by theresponsible ordnance officer.
129. Records
a. The principal records pertaining to the weaponare the weapon record book (DA Form 9-13 andDA Form 9-13-1), a field report of accidents (AR385-63), and the unsatisfactory equipment report(DA Form 468). Information on the purpose anduse of these records may be found in the recordsthemselves.
AGO 2790OC 85
b. The principal records pertaining to the motorcarriage are the vehicle technical manual, lubrica-tion order, accident report (DA Form 285), andvehicle and equipment operational record (DD Form110). Information on the purpose and use of theserecords may be found in the records themselves.
c. The chiefs of sections and the battery executivealso should keep semipermanent records on theweapons and vehicles for information and guidance.
130. Maintenance
For detailed instructions concerning maintenanceof the howitzer and carriage, see TM 9-324A andTM 9-717A.
131. Inspections
Regular inspections are required to insure thatmateriel is maintained in serviceable condition.
a. The chief of section is responsible for all ofthe equipment in his section. He should inspect itthoroughly each day. If he sees the need for repairor adjustment that the section cannot remedy, henotifies the executive immediately so that the neces-sary action may be taken.
b. The battery executive, accompanied by theartillery mechanic, should make a daily spot checkinspection. He inspects different parts of the weap-ons and carriages each day to insure complete cov-erage every few days. At least once a month thebattery executive makes a thorough mechanical in-spection of weapons, motor carriages, auxiliaryequipment, tools, and spare parts.
86 AGO 2790C
c. Battery, battalion, and higher commandersshould make frequent command inspections to as-sure themselves that the equipment in their com-mands is being maintained at prescribed standardsof appearance, condition, and completeness.
d. For details on inspecting the howitzer and car-riage, see TM 9-324A and TM 9-717A.
e. Duties of individuals in performing the neces-sary inspection and maintenance of the weapon andcarriage are given in tables V and VI.
AGO 2790Q 87
CHAPTER 10
DECONTAMINATION OF EQUIPMENT
132. GeneralEquipment which has been contaminated by bio-
logical, chemical, or radiological agents constitutes adanger to personnel. Contamination means thespreading of an injurious agent in any form andby any means. Persons, objects, or terrain can becontaminated. Decontamination is the process ofmaking any contaminated place or thing safe forunprotected personnel. This can be done by cover-ing, destroying, removing, or changing into harm-less substances the contaminating agent or agents.Generally, only equipment contaminated by per-sistent agents need be decontaminated.
133. Decontamination for Chemical Agents
a. Ammunition. With rags, wipe off visible con-taminant from projectiles. Apply DANC (decon-tamination agent, noncorrosive, M4), wipe withsolvent-soaked rag, and then dry. If DANC is notavailable, scrub with soap and cool water. Slurry(equal weights of water and chloride of lime) canbe used on contaminated ammunition containers,but it must not be allowed to penetrate into the am-munition itself.
b. Instruments. If instruments are exposed tocorrosive gases, clean them as soon as possible with
as AGO 2790C
solvent, allow them to aerate, and apply a thin coatof light machine oil. A rag dampened with DANCmay be used, followed by drying with a clean ragand then applying a coat of machine oil. DANCinjures clear plastic or hard rubber surfaces.
c. Weapons. Remove dirt, dust, grease, and oilfrom weapons. Do not apply wet mix but allow sur-faces to air after oil and dirt have been removed.DANC can be used on all metal surfaces exceptthe bore. Also effective on metal are hot water andsoap or cleaning solvent. After decontamination,weapons are dried and oiled.
d. Automotive Equipment. Light contaminationfrom spray can be decontaminated by aeration alone.For heavier contamination, use DANC on exterioror interior surfaces which personnel are likely totouch. For larger area decontamination, wash ve-hicle with water and scrub painted surfaces withsoap and water.
134. Decontamination for Biological and RadiologicalAgents
a. General. After a contaminating attack, recov-ery of equipment may be achieved either by waiting,to permit the decay of contamination, or by activedecontamination to reduce the danger to a levelwhere it is no longer a significant hazard to oper-ating personnel. Decontamination may be eitherrough or detailed, depending on the urgency of themilitary situation. The procedure adopted will bea command decision.
AGO 2790C 89
b. Rough Decontamination. Rough decontamina-tion is performed when urgency is the main factor.Its purpose is to reduce contamination sufficiently topermit personnel to work with, or close to, equipmentfor limited periods. Rough decontamination may beachieved by means of water or steam, if available.Soap or other detergent used in conjunction withwater or steam aids in decontamination.
c. Detailed Decontamination. Detailed decontami-nation, in which the emphasis is on thoroughness,will be carried out in rear areas and repair basesand include procedures of surface decontamination,aging, sealing, and disposal.
135. References
For further information on decontamination, seeFM 21-40 and TM 3-220.
90 AGO 2790C
CHAPTER 11
DESTRUCTION OF EQUIPMENT
136. Generala. Tactical situations may arise in which it is nec-
essary to abandon equipment in the combat zone.In such a situation all abandoned equipment must bedestroyed to prevent its use by the enemy.
b. The destruction of equipment subject to captureor abandonment in the combat zone will be under-taken only upon authority delegated by a division orhigher commander.
137. PlansAll batteries will prepare plans for destroying
their equipment in order to reduce the time requiredshould destruction become necessary. The principlesto be followed are-
a. Plans for destruction of equipment must be ade-quate, uniform, and easily carried out in the field.
b. Destruction must be as complete as the availabletime, equipment, and personnel will permit. Sincecomplete destruction requires considerable time,priorities must be established so that the more es-sential parts are destroyed first.
c. The same essential parts must be destroyed onall like units to prevent the enemy from constructinga complete unit from undamaged parts.
AGO 2790C 91
d. Spare parts and accessories must be given thesame priorities as the parts installed on the equip-ment.
138. Methods
To destroy equipment adequately and uniformly,all personnel of the unit must know the plan andpriority of destruction and be trained in the methodsof destruction.
139. References
For detailed information on destruction of the105-mm howitzer M52, self-propelled, complete withfire control equipment and spare parts, see TM 9-717A. For destruction of ammunition, see TM 9-1901.
92 AGO 2790C
CHAPTER 12
SAFETY PRECAUTIONS
140. General
Safety precautions to be observed in training areprescribed in AR 385-63. Additional information isfound in FM 6-140, TM 9-324A, TM 9-717A, TM9-1900, and TM 9-1901. The more important safetyprecautions are summarized in paragraphs 141through 143.
141. Ammunition
a. All ammunition on the ground at the firing posi-tion must be so placed that it is protected againstexplosion in case of accident at the position. Fireand explosive or flammable materials must be keptaway from ammunition. Ammunition should be pro-tected from direct rays of the sun by use of a tar-paulin or other suitable covering.
b. Battery personnel must not attempt to disas-semble fuzes.
c. If for any reason a round is not fired after thetime fuze has been set, the fuze must be reset toSAFE before it is restowed.
d. All rounds not fired which have been preparedfor firing must be checked by the chief of section toinsure that all seven powder increments are presentin proper order and condition and that they are of
AGO 2790C 93
the proper lot number. The chief of section alsoverifies that the lot number on the projectile and thecartridge case corresponds to the lot number onthe container. For ammunition that is to be re-turned to ordnance, a battery officer must certifythat it has been properly reassembled (FM 6-140).
142. Misfires
a. In the event of a misfire, two more attempts aremade to fire the howitzer. Wait 2 minutes beforebreach is opened.
Caution: The howitzer should remain as laid andall personnel must stay clear of the muzzle and pathof recoil. All personnel not required for the opera-tion should be cleared from the vicinity.
b. After the third attempt to fire the howitzer hasbeen made, the command to unload (par. 105) isgiven. The breach is opened to extract the cartridgecase. Should the complete round be extracted, theprojectile is separated from the cartridge case. Theprimer in the base of the cartridge case is immedi-ately inspected to determine whether the indent isnormal. If there is normal indentation, the cartridgecase is thrown clear of all personnel to prevent in-jury in case of a hangfire. The projectile is reloadedwith another cartridge case and firing is resumed.
c. See TM 9-324A for action to be taken in casethe indent on the primer is light or there is no in-dent, which indicates that the firing lock is not func-tioning properly.
d. See TM 9-324A for safety regulations pertain-ing to misfires.
94 AGO 2790C
143. General Safety Precautions During Drill and Firing
a. The howitzer is kept unloaded except when fir-ing is imminent.
b. Members of the section on the ground will passin rear of the carriage when they go from side toside.
c. Personnel should stay a safe distance from thebreech to prevent injury when the gun recoils.
d. During firing, personnel should use cotton intheir ears to protect eardrums against injury.
e. In training, there must always be a safety offi-cer for each artillery unit firing. For duties of thesafety officer, see FM 6-40.
AGO 2790C 95
CHAPTER 13
TRAINING
Section I. GENERAL
144. Purpose and Scope
The purpose of this chapter is to present the abso-lute minimum requirements for training the person-nel of a howitzer section in the performance of theirduties in service of the howitzer. It includes generalinformation on the conduct of training, a minimumtraining schedule, and tests to be given for the quali-fication of gunners.
145. Objectives
The objectives of training are to speed the at-tainment of proficiency by cannoneers in their indi-vidual duties and, through drill, to weld them intoan effective, coordinated team that is able to func-tion efficiently in combat. During training, super-visors should keep in mind the proficiency soughtby the appropriate Army Training Tests. Maxi-mum efficiency is attained through regular drills.
146. Conduct of Traininga. Training will be conducted in accordance with
the principles set forth in FM 21-5. The goal oftraining should be the standards set forth in FM 6-125 and AR 611-201.
96 AGO 2790C
b. In general, individual training is conducted bynoncommissioned officers as far as practicable. Offi-cers are responsible for preparing training plans,for conducting unit training, and for supervisingand testing individual training.
c. Throughout training, the application of priorinstruction to current training must be emphasized.
d. A record of the training received by each indi-vidual should be kept on a progress card which maybe maintained by each chief of section for each manin his section. This card should show each periodof instruction attended, tests taken, and remarkspertaining to progress. Progress cards should beinspected frequently by the battery executive tomake sure they are being kept properly and to de-termine the state of training. Requiring the chiefof section to keep these records emphasizes his re-sponsibility toward his section.
e. The necessity for developing leadership and ini-tiative in noncommissioned officers must be em-phasized constantly throughout training.
147. Standards To Be Attained
A satisfactory trained howitzer section is one inwhich each member knows the duties of all othermembers of the section and is able to perform effi-ciently in all positions. See chapter 14 for tests tobe given for the qualification of gunners.
AGO 2790C 97
Section II. MINIMUM TRAINING SCHEDULE
148. General
The training schedule given in paragraph 150 isa guide to meet the minimum training require-ments in subjects covered in this manual for per-sonnel of a howitzer section.
149. Individual Periods
a. Individual periods of training in service of thepiece should be arranged along with other batterytraining into a balanced training program, takinginto consideration the basic principles of training.
b. In general, except for service practice, periodson any subject should not be longer than 1 hour.Howitzer drill periods should be for 1/2 hour onlyand should be conducted in a vigorous manner.
c. Periods of howitzer drills should be precededand followed by periods on subjects that will belogically related to the drill. For example, a periodof howitzer drill should be preceded by a period oftesting and adjustment of sighting and fire controlequipment and followed by a period on inspectionand maintenance drills. A period on aiming postdisplacement correction may be presented betweentwo periods of howitzer drill.
d. TM 9-324A provides information on which tobase periods of instruction on description, charac-teristics, and functioning of the howitzer; familiar-ization with the howitzer, including breech and fir-ing mechanism, tube assembly and top carriage,
98 AGO 2790C
recoil mechanism, elevating mechanism, and sight-ing and fire control equipment; and field assemblyand malfunction. These periods of instruction shouldbe included in the battery training schedule, closelyallied with the training in service of the piece givenin paragraph 150. Approximately 8 hours shouldbe devoted to this instruction.
e. Additional service of the piece training may beperformed during battery training exercises.
AGO 2790C 99
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CHAPTER 14
TESTS FOR QUALIFICATION OF GUNNERS
Section I. GENERAL
151. Purpose and Scope
This section prescribes the tests to be given in thequalification of gunners. The purpose of the testsis twofold:
a. To provide a means of determining the rela-tive proficiency of the individual artillery soldier inthe performance of the duties of the gunner, 105-mm howitzer M52, self-propelled. The tests will notbe a basis for determining the relative proficiencyof batteries or higher units.
b. To serve as an adjunct to training.
152. Standards of Precision
The candidate will be required to perform thetests in accordance with the standards in a throughd below.
a. Scale settings must be exact, and matching in-dexes must be brought into coincidence.
b. Level bubbles must be exactly centered.c. The vertical cross hair in the reticle of the pan-
oramic telescope must be alined on the left edge ofthe aiming post or on exactly the same part of theaiming point each time the howitzer is laid.
102 AGO 2790C
d. Final motions of azimuth and elevation settingknobs, as well as traversing and elevating hand-wheels, must be made in the appropriate direction.For elevating, the final motion of the handwheelshould be in the direction of the more difficult move-ment. Final motion for traversing is from left toright. Final movement of the vertical cross hair ofthe telescope is from left to right.
153. Assistance
The candidate will receive no unauthorized assist-ance. Each candidate may select authorized assist-ants as indicated in the tests. In the event a candi-date fails any test through the fault of the examineror any assistant, the test will be disregarded, andthe candidate will be given another test of the samenature.
154. Time
The time for any test will be the time from the lastword of the command to the last word of the candi-date's report. The candidate may begin any testafter the first word of the first command.
155. Scoring
Scoring will be accordance with the two para-graphs, Penalties and Credit, under each subject.If a test is performed correctly, credit will be givenin accordance with the paragraph Credit under eachsubject. No credit will be allowed if conditions existas specified in paragraph titled Penalties.
AGO 2790C 103
156. Preparation for Tests
The howitzer will be prepared for action and thecandidate posted at the proper position correspond-ing to the test being conducted or as indicated inparagraph entitled Special Instructions. The exam-iner will insure that the candidate understands therequirements of each test and will require the can-didate to report "I am ready," before each test.
157. Qualification Scores
Minimum scores required for qualification in thecourses are as follows:Individual classification PointsExpert gunner --------------------------------- 90First-class gunner ------------------------------ 80Second-class gunner ----------------------------- 70
158. Outline of Tests
Num. MaxiSection ber of Points mum
No. Subject tests each credit
II Direct laying, direct fire tele- 4 2 8scope.
III Indirect firing, deflection 18 2 36only.
IV Displacement correction- 1 4Part I (3) (3)Part II (1) (1)
V Measuring deflection. 2 4 8VI Laying for elevation, elevation 3 2 6
counter.VII Laying for elevation, gunner's 3 2 6
quadrant.VIII Measuring the elevation. 1 5 5IX Measuring site to mask. 1 4 4
104 AGO 2790C
Num- Maxi-Section ber of Points mum
No. Subject tests each credit
X Tests and adjustment of sight- 2 4 8ing and fire control equip-ment.
XI Materiel. 3 5 15
Total credit 100
Section II. TEST, DIRECT LAYING, DIRECT FIRE TELESCOPE
159. Scope of Tests
a. Four tests (2 groups of 2 tests each) will beconducted in which the candidate will be requiredto execute commands similar to those in paragraph161.
b. Tests 1 and 2 (and tests 3 and 4) will be exe-cuted as one series of commands.
c. The candidate will be tested in the duties of thegunner.
160. Special Instructions
a. A stationary target will be placed approxi-mately 600 yards from the howitzer.
b. Coarse azimuth and micrometer scale will beset at zero, and indexes will be matched.
c. Candidate will be posted as the gunner.
d. Howitzer will be pointed so that a shift of ap-proximately 100 mils will be required for tests 1 and
AGO 2790C 105
3, and it will not be necessary to shift the motorcarriage for any of the 4 tests.
e. Laying at the termination of tests 1 and 3 willnot be disturbed prior to beginning tests 2 and 4.
f. Examiner will announce the assumed directionof the movement of the target at the beginning oftests 1 and 3. The assumed direction of the move-ment of the target in test 3 will be opposite to thatin test 1.
161. Outline of Test
Test Examiner commandsNo. (for example) Action of candidate
1 and 3 TARGET, THAT Centers cant corrector bubbles.TANK; FROM Traverses tube until properLEFT TO RIGHT, lead has been set.LEAD 5, RANGE Places proper range line of600. reticle on the center of the
visible mass of the target.Gives the command, FIRE,
when ready and steps clear.2 and 4 RIGHT (LEFT) Same as test 1 above.
10, ADD (DROP)200.
162. Penalties
No credit will be allowed if, after each test-a. Azimuth scale has been moved from zero.b. Indexes on the azimuth micrometer have been
moved from zero.c. Cant corrector bubbles on the telescope mount
are not centered.
106 AGO 2790C
d. Lead in mils is not set properly.
e. Proper range line of the reticle is not on thecenter of the visible mass of the target.
163. Credit
Time in seconds, exactly or less than_4 4% 5Credit -__________________________2.0 1.5 1.0
Section III. TEST, INDIRECT FIRING, DEFLECTION ONLY
164. Scope of Tests
Eighteen tests will be conducted in which the can-didate will be required to execute commands similarto those in paragraph 166. Tests 1 through 4 (andtest 5 through 9, 10 through 13, and 14 through 18)will be executed as one series of commands.
165. Special Instructions
a. Commands will not necessitate manual shift-ing of the howitzer beyond the limits of on-carriagetraverse.
b. Examiner will select a suitable aiming pointand identify it to the candidate.
c. Commands for special corrections will be givenonly in the tests indicated in paragraph 166.
d. Command for new deflections for each test willbe within the following prescribed limits:
AGO 2790C 107
Maximum Minimumchange change
Test No. (mils) (mils)
2 and 11 -------------------------- 180 1403 and 12 -------------------------- 90 704 and 13 ------------ - 40 207 and 16 ----------- _---_---------- 100 608 and 17 -------------------------- 50 309 and 18 -------------------------- 20 10
e. Piece will be laid with correct settings at theconclusion of each test before proceeding with thenext test.
f. Aiming posts will be set out at prescribed de-flection and distances for these tests.
g. Examiner will designate the numbered sectionto be used. The examiner will announce special cor-rections in deflection to be applied by the candidate.
h. Candidate will be posted as the gunner.
108 AGO 2790C
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167. Penalties
No credit will be allowed if, after each test-
a. Deflection is not set correctly.
b. Leveling mechanism bubbles are not centered.
c. Vertical cross hair of the telescope is not on theaiming point or left edge of aiming posts, as the casemay be.
d. Last motion of the traverse was not made to theright.
168. Credit
Time in seconds, exactly or less than-Tests 1, 10, 6, and 15 each-----_12 13 14Other tests, each ____________-- 8 9 10
Credit _--------------------------- 2.0 1.5 1.0
Section IV. TEST, DISPLACEMENT CORRECTION
169. Scope of Test
One test, consisting of two parts, will be conductedin which the candidate will be required to executethe commands given in paragraph 171.
170. Special Instructions
a. Aiming posts will be set out at the prescribeddistances.
b. An assistant, selected by the candidate, will bestationed close to the far aiming post.
c. Examiner will require the candidate to lay thehowitzer on an announced deflection and report, "Iam ready."
AGO 2790C 111
d. The far aiming post or the howitzer will thenbe moved so that a displacement of 5 to 10 milsoccurs.
e. Laying of the howitzer at the termination ofpart I will not be disturbed for part II.
171. Outline of Tests
a. Part I.
Examinercommands I Action of candidate
CORRECT Lays the howitzer so that the far aimingFOR DIS- post appears midway between the nearPLACE- aiming post and the vertical cross hairMENT. of the reticle of the telescope.
Checks centering of bubbles.Re-lays if necessary.Calls "Ready" and steps clear.
b. Part II.
Examinercommands Action of candidate
ALINE AIM- Records deflection on breech and announcesING POSTS. "Deflection (so much) recorded."
Directs assistant in alining aiming posts.Calls "Ready" and steps clear.
172. Penalties
No credit will be allowed for either part if-
a. Part I.(1) Far aiming post does not appear midway
112 AGO 2790C
betweeen the near aiming post and thevertical cross hair of the telescope.
(2) Level bubbles are not centered.(3) Last motion of traverse was not made to
the right.b. Part II.
(1) Deflection is not the announced deflection.(2) Aiming posts are not properly alined.(3) Vertical cross hair of the telescope is not
on the left edge of the aiming posts.
173. Credit
Part I, time in seconds, exactly 3 3Y3 32% 4or less than.
Credit --- __________________ 3.0 2.0 1.5 1.0Part II, no time limitCredit --- …___--- ___________ 1.0
Section V. TEST, MEASURING DEFLECTION
174. Scope of Test
Two tests will be conducted in which the candi-date will be required to measure and report a de-flection in accordance with the commands in para-graph 176.
175. Special Instructions
a. Howitzer will be laid on aiming posts to theright front.
b. Examiner will select two aiming points. Theaiming point for test 1 will be within 200 mils to theleft or right of the aiming posts; and the aiming
AGO 2790C 113
point for test 2 will be within 200 mils on the oppo-site side of the aiming posts.
c. The appropriate aiming point will be designatedby the examiner and identified by the candidateprior to the start of each test.
176. Outline of Test
TestNo. Examiner commands Action of candidate
1NO. 1, AIMING Centers leveling mechanism
POINT, CHURCH bubbles.STEEPLE TO Refers to aiming point.LEFT FRONT, Checks centering of bubblesREFER. and re-lays telescope if
necessary.Reads deflection and reports
"No. (so-and-so) deflection2 (so much)" and steps clear.
NO. 1, AIMING Same as test 1 above.POINT, WATERTOWER, RIGHTFRONT, REFER.
177. Penalties
No credit will be allowed if-
a. Leveling mechanism bubbles are not centeredproperly.
b. Vertical cross hair of the telescope reticle isnot on the aiming point.
c. Deflection is not announced correctly.
d. Traversing handwheel is turned.
114 AGO 2790C
178. Credit
Time in seconds, for each test, 5 5% 6 6%exactly or less than.
Credit ______---- _------------ 4.0 3.0 2.0 1.5
Section VI. TEST, LAYING FOR ELEVATION, ELEVATIONCOUNTER
179. Scope of Test
Three tests will be conducted in which the candi-date will be required to execute commands similarto those in paragraph 181.
180. Special Instructions
a. Each test will require a change of settings andthe accompanying laying of the tube in elevation.(All commands given will be within the limits of200 to 400 mils on the elevation counter.)
b. Commands for elevation for tests 2 and 3 willnot be made in multiple of 5 mils.
181. Outline of Test
Test Examiner commandsNo. (for example) Action of candidate
1 ELEVATION 290. Sets announced elevation.Matches elevation counter
vernier.Checks level bubbles.Calls "Ready."
2 ELEVATION 326. Same as test 1 above.3 ELEVATION 323. Same as test 1 above.
AGO 2790C 115
182. Penalties
No credit will be allowed, if after each test-
a. Elevation counter is not set accurately.
b. Elevation counter vernier is not matched.
c. Last motion of the tube was not in the directionin which it is most difficult to turn the elevatinghandwheel.
183. Credit
Time in seconds, exactly or less than_ 6% 7% 8%Credit …______________-____-______ 2.0 1.5 1.0
Section VII. TEST, LAYING FOR ELEVATION, GUNNER'SQUADRANT
184. Scope of Tests
Three tests will be conducted in which the can-didate will be required to execute commands similarto those in paragraph 186.
185. Special Instructions
a. Gunner's quadrant will be set at zero for thefirst test.
b. Each succeeding test will require a change ofquadrant setting within the limits of 30 to 60 mils.
c. Candidate will be posted to the left of andfacing the breech, with the gunner's quadrant inhis hand.
d. An assistant, selected by the candidate, will beposted to operate the elevating handwheel.
116 AGO 2790C
186. Outline of Tests
Test Examiner commandsNo. (for example) Action of candidate
1 QUADRANT 190. Sets quadrant elevation ongunner's quadrant. Seatsquadrant.
Has assistant elevate or de-press the tube until quad-rant bubble is centered.
Calls "Ready" and waits forexaminer to verify laying.
2 QUADRANT 245. Same as test 1 above.3 QUADRANT 215. Same as test 1 above.
187. Penalties
No credit will be allowed if, after each test-
a. Quadrant elevation is not set correctly.
b. Quadrant is not properly seated.
c. Quadrant bubble is not properly centered.
188. Credit
Time in seconds, exactly or less than_ 6 6% 7Credit ------------------------- _ 2.0 1.5 1.0
Section VIII. TEST, MEASURING ELEVATION
189. Scope of Test
One test will be conducted in which the candidatewill be required to measure the elevation by meansof the gunner's quadrant.
AGO 2790C 117
190. Special Instructions
Prior to the test the examiner will lay the tubeat a selected elevation, measure the elevation, andthen set the gunner's quadrant at zero.
191. Outline of Test
Examinere,,lnmands Action of candidate
MEASURE Places gunner's quadrant on the quadrantTHE ELE- seats of the breech ring.VATION. Levels bubble by raising or lowering the
index arm and turning the micrometerknob.
Announces "No. (so-and-so), elevation (somuch)," and hands quadrant to examiner.
192. Penalties
No credit will be allowed if-
a. Quadrant bubble is not centered when the quad-rant is seated properly.
b. Elevation is not announced correctly.
193. Credit
Time in seconds, exactly or less than_ 8 9% 10%Credit ------------------------- __ 5.0 3.5 2.0
Section IX. TEST, MEASURING SITE TO MASK
194. Scope of Test
One test will be conducted in which the candidatewill be required to execute the command given inparagraph 196.
118 AGO 2790C
195. Special Instructions
a. The howitzer, prepared for action, will beplaced 200 to 400 yards from a mask of reasonableheight.
b. The tube will be pointed so that it is 100 to 150mils above the crest and 100 to 150 mils right or leftof the highest point of the crest.
c. An assistant, selected by the candidate, will bestationed as the gunner to elevate or depress thetube as required by the candidate.
d. The candidate will take post at the rear of thebreech.
196. Outline of Test
Examinercommands j Action of candidate
MEASURE Sights along lowest element of bore andSITE TO directs operation of the elevating andMASK. traversing mechanism until line of site
just clears the crest.Rotates the elevation counter setting knob
until the vernier is alined and elevationcounter is set.
Checks centering of level bubbles.Reads elevation from elevation counter.Reports "No. (so-and-so), site to mask (so
much) ."
197. Penalties
No credit will be allowed if-
a. Line of sight along the lowest element of thebore does not just clear crest.
AGO 2790C 119
b. Vernier is not accurately alined.
c. Site to mask is not announced correctly.
198. Credit
Time in seconds, exactly or less than_ 11 12 13 14Credit --------------------------- 4.0 3.0 2.0 1.5
Section X. TESTS AND ADJUSTMENT OF SIGHTING ANDFIRE CONTROL EQUIPMENT
199. Scope of Test
Two tests will be conducted in which the candidatewill be required to demonstrate the methods em-ployed in making the prescribed tests and authorizedadjustments or to describe the action to be taken(e.g., send to ordnance) if adjustment is not au-thorized to be made by using personnel.
200. Special Instructions
a. Howitzer will be prepared for the test by level-ing the trunnions and centering the tube in traverse.Cross hairs will be installed on the muzzle, andeither the breech boresight inserted or the firingmechanism removed.
b. Equipment required for the tests will includecross hairs for the muzzle (breech boresight op-tional), gunner's quadrant, plumb line or transit,and testing target.
c. Candidate will select an assistant who will op-erate the elevating handwheel and adjust and alinethe testing target at the direction of the candidate.
120 AGO 2790C
d. Tests will be conducted in the chronological se-quence indicated in paragraph 201. After comple-tion of test 2, the gunner's quadrant used in tests1 and 2 will be used for test 3, with the propercorrection, as determined in test 1, carried on thequadrant, provided the correction does not exceed0.4 mil.
e. Adjustments which the candidate may be re-quired to accomplish will fall within the followinglimits:
(1) Reticle (zero cross) direct fire telescopewithin limits of boresight adjustment.
(2) Vertical line of reticle of panoramic tele-scope.
f. The tube will be leveled at the conclusion of test2 and will not be disturbed thereafter.
201. Outline of Tests
TestNo. Examiner commands I Action of candidate
1 PERFORM END- Performs test as prescribed inFOR-END TEST paragraph 122.ON GUNNER'S Calls "Error (so many) mils,QUADRANT. quadrant serviceable (un-
serviceable)" and handsquadrant to examiner forverification.
2 PERFORM Performs test as prescribed inMICROMETER paragraph 123.TEST ON GUN- Calls "Quadrant micrometer isNER'S QUAD- (is not) in error."RANT.
AGO 2790C 121
202. Penalties
The tests are not essentially speed tests. The pur-pose of the prescribed time limits is to insure thatthe candidate can perform the operation withoutwasted effort. No credit will be allowed for tests1 and 2 if-
a. Test 1.(1) Bubble of the gunner's quadrant does not
center when verified by the examiner.(2) The error (one-half of the amount of the
angle which was indicated when the quad-rant was first reversed and the bubble cen-tered by moving the index arm and mi-crometer) is not announced correctly bythe candidate.
(3) Candidate does not declare the quadrantunserviceable if the error (necessary cor-rection) exceeds 0.4 mil.
(4) Time to complete the test exceeds 2 min-utes.
b. Test 2.(1) Procedure is not followed correctly.(2) Time to complete the test exceeds 1 min-
ute.
203. Credit
a. Candidate will be scored on the general meritof his work in addition to the specific requirementsabove.
b. If the tests are performed correctly within the
122 AGO 2790C
prescribed time limit, maximum credit will be givenas follows:
Test 1 -----__________--______------------------ 4Test 2 …____________________________________ 4
Total _______________---------------------- 8
Section XI. TEST FOR MATERIEL
204. Scope of Test
Candidate will be required to perform three testsas outlined in paragraph 206.
205. Special Instructions
a. Tests 1 and 2. For tests 1 and 2, a paulin willbe placed on the carriage for the convenience of thecandidate in laying out the disassembled parts. Thecandidate will be allowed to select the tools and ac-cessories necessary for the performance of the testsprior to the start of the tests.
b. Test 3. For test 3, a complete set of lubricationequipment authorized for use of battery personnelwill be made conveniently available on a paulin ad-jacent to the howitzer. Every type of lubricant usedon the howitzer will be placed conveniently on thepaulin, each in a plainly labeled container, and thelubrication order for the howitzer will be madeavailable for use of the candidate.
AGO 2790C 123
206. Outline of Tests
TestNo. Examiner commands Action of candidate
1 PERFORM AU- Performs the operation as de-THORIZED DIS- scribed in TM 9-324A, lay-ASSEMBLY OF ing the parts on the paulin.BREECH ME- After disassembly, identifiesCHANISM AND all parts to examiner.FIRING LOCK.
2 ASSEMBLE Performs the operation as de-BREECH ME- scribed in TM 9-324A.CHANISM ANDFIRING LOCK.
3 DAILY, WEEKLY, Using the lubrication order asAND MONTHLY a guide, selects proper lubri-LUBRICATION cating equipment and lubri-TEST. cant and shows how and
with which lubricant eachlubrication point is serviced.(Actual lubrication is notperformed.)
207. Penalties
a. The tests are not essentially speed tests. Thepurpose of the maximum time limits is to insure thatthe candidate can perform the operations withoutwasted effort.
b. No credit will be given if the following timelimits are exceeded:
Test 1 --------------------------_-__ 1% minutesTest 2 --_--------_----------------_- 3 minutesTest 3 ------------------------------ 2 minutes
c. A penalty of one-half point will be assessed foreach component part that is not correctly identified
124 AGO 2790C
or omitted in test 1. There is no time limit imposedon the identification of component parts. However,the examiner may reduce the grade if it becomesobvious that the candidate is not familiar with thenomenclature.
208. Credit
a. The candidate will be scored on the generalmerit of his work in addition to the specific re-quirements stated in paragraph 207.
b. If each test is performed correctly within theprescribed time limit, maximum credit will be givenas follows:
Test 1 ----_---------------------------…----- 5Test 2 __…____-- ____--____--__-----_--------- 5Test 3 _--____-- ____--___---___--___---____-- 5
Total ___---------------------------------- 15
AGO 27900 125
APPENDIX
REFERENCES
1. Miscellaneous Publications
AR 385-63 Regulations for Firing Am-munition for Training, Tar-get Practice, and Combat.
AR 600-70 Badges.AR 611-201 Manual of Enlisted Military
Occupational Specialties.AR 700-38 Unsatisfactory Equipment
Report (Reports ControlSymbol CSGLD-247 (R2)).
AR 750-5 Maintenance Responsibilitiesand Shop Operations.
ATP 6-300 Army Training Program forField Artillery Unit (U).
ATT 6-1 Training Tests for Field Ar-tillery Howitzer or GunBattery.
ATT 6-2 Training Tests for Field Ar-tillery Battalion Firing.
ATT 6-3 Training Tests for Field Ar-tillery Rocket Battery andBattalion Tests.
DA Pam 108-1 Index of Army Motion Pic-tures, Television Record-ings, and Filmstrips.
126 AGO 2790C
DA Pam 310-series Index of Military Publica-tions.
SR 320-5-1 Dictionary of United StatesArmy Terms.
SR 320-50-1 Authorized Abbreviations.TOE 6-317C Armored Field Artillery Bat-
tery, 105-mm Howitzer,Self-Propelled or HowitzerCompany, Armored Cav-alry Reconnaissance Bat-talion.
FM 5-15 Field Fortifications.FM 5-20 Camouflage, Basic Principles.FM 5-20B Camouflage of Vehicles.FM 5-20D Camouflage of Field Artillery.FM 5-25 Explosives and Demolitions.FM 6-40 Field Artillery Gunnery.FM 6-101 The Field Artillery Battalion.FM 6-125 Qualification Tests for Spe-
cialists, Field Artillery.FM 6-140 The Field Artillery Battery.FM 17-50 Logistics, Armored Division.FM 21-5 Military Training.FM 21-30 Military Symbols.FM 21-40 Defense Against CBR Attack.FM 21-60 Visual Signals.FM 22-5 Drills and Ceremonies.FM 23-65 Browning Machine Gun, Cal-
iber .50 HB, M2.FM 25-10 Motor Transportation, Opera-
tions.LO 9-7204 Howitzer, 105-mm Self-Pro-
pelled, T98E1.
AGO 2790C 127
TM 3-220 Decontamination.TM 6-605 Field Artillery Individual and
Unit Training Standards.TM 9-324A 105-mm Howitzer T96E1.TM 9-575 Auxiliary Sighting and Fire
Control Equipment.TM 9-717A Self-Propelled 105-mm How-
itzer T98E1.TM 9-850 Abrasive, Cleaning, Preserv-
ing, Sealing, Adhesive, andRelated Materials Issuedfor Ordnance Materiel.
TM 9-1527 Gunner's Quadrants M1 andM1918 and Machine GunClinometer M1917.
TM 9-1590 Fuze Setters, M14, M22, M23,M25, and M27.
TM 9-1900 Ammunition, General.TM 9-1901 Artillery Ammunition.TM 9-2300 Artillery Materiel and Asso-
ciated Equipment.TM 9-2810 Tactical Motor Vehicle Inspec-
tions and Preventive Main-tenance Services.
TM 9-2853 Preparation of Ordnance Ma-teriel for Deep Water Ford-ing.
TM 21-301 Driver Selection, Trainingand 'Supervision, Half-Track and Full-Track Ve-hicles.
TM 21-305 Driver's Manual.
128 AGO 2790C
TM 21-306 Manual for the Full-Track Ve-hicle Driver.
DA Form 9-13 Weapon Record Book.DA Form 468 Unsatisfactory Equipment
Report.
2. ORD Supply Manuals
ORD 9 SNL G-258 Howitzer, 105-mm, Self-Pro-pelled, T98E1.
ORD 3 SNL K-1 Abrasives, Adhesives, Clean-ers, Preservatives, RecoilFluids, Special Oils and Re-lated Items.
ORD 3 SNL R-1 Ammunition, Fixed and Semi-fixed, Including Subcaliberfor Pack, Light and Me-dium Field, Aircraft, Tank,and Antitank Artillery, In-cluding Complete RoundData.
ORD 3 SNL R-3 Ammunition, Service Fusesand Primers for Pack,Light and Medium Field,Aircraft, Tank, and Anti-tank Artillery.
SM 9-5-1375 Ammunition Explosives, BulkPropellants, and ExplosiveDevices.
AGO 2790C 129
INDEX
Paragraphs Page
Action, to prepare ____________.----------- 10 13Aiming:
Points ____-------------------------- 99 59Posts ______________________________. 100 60Posts, displacement correction _______-- 101 62
Ammunition:Care----__________________________-- 106 67Safety precautions-____-_____________. 141 93
Basic periodic tests:Equipment -- ________-______________. 110 70General __----__--- ___-- _____________ 116 80Test:
Elevation counter synchronization__. 119 81Fuse setters ____________________. 126 84Gunner's quadrant --______________ 121-125 82Panoramic telescope T149E1 and 120 82
T150E1.Telescope mount T179 -__________ 117, 118 81
Battery, in, definition---_________________ 2 4Board, section data ___________________--- 107 69Boresighting:
Condition -__________________________ 112 72Distant aiming point method--_________ 114 76Equipment __________________________ 110 70General_____________________________ 111 71Standard angle method ------ _________ 115 76Testing target method --------________ 113 72
Call off ________________________________. 9 11Cannoneers, general duties --_--__________. 6 8Cant, to correct---____.__________________.- 93 56Capabilities of motor carriage____________ - -3 5
130 AGO 27900
Paragraphs Page
Cease firing___ __------------------------- 103 64Change posts ---------------------------- 11 16Changes in data during firing -------------- 104 66Composition of howitzer section__----------- 5 8Conduct of training ________-------------- 146 96
Data, board section ____------------------ 107 69Decontamination:
Biological and radiological ------------- 134 89Chemical agents---------------------- 133 88General _____-- _-------------------- 132 88References ________________________.. 135 90
Definitions and terms _____-______________ 2 4Destruction of equipment:
General----_________________________ 136 91Methods ____________-_______________ 138 92Plans ______________________________ 137 91References _-----___________________. 139 92
Direct laying using telescope T150E1________ 81 58Disassembly, adjustments, and assembly by 128 85
battery personnel.Dismount___ -------------------------- -_ 13 17Dismounted posts ----------------________ 13 17Displacement corrections, aiming post ----_ _ 101 62Distant aiming point method (boresighting)__ 114 76Duties:
Chief of section (direct fire) -------- ___ 83-91 53Gunner (direct fire) ------------------ 92-95 56In firing:
Chief of section------------------. 21 22Driver __----------------------- 71 43Gunner ____--------------------. 37 28No. 1 ___----------------------- 47 35No. 2______---------------------. 54 37No. 3_________ ______----------- . 57 37No. 4__-------------------------. 62 40No. 5 --------------------------- 66 42
AGO 2790C 131
Paragraphs PageDuties-Continued
In inspection:After operation _____------------ . 131 86Before operation ____------------. 131 86During halt---------------------- 131 86
In march order____________-------- ----------- 17 20In prepare for action ______--- __---- _. 16 19No. 1 (direct fire) ___________________- -96 57Of individuals (in firing) ____-_-------- 20 21Of personnel, general …________________. 6 8Remainder of section (direct fire) -______ 92-97 56
Equipment, description ___________________ 3 5
Fall:In________________________________ -- 9 11Out ________________________________ 14 17
Field of fire (direct fire) -_________________ 76 45Fire:
Field of (direct fire) __________--______ 76 45Priority of (direct fire targets) - -_______ 77 45
Firing, cease ------------------__________ 103 64Form the section ________________________ 9 11Front, definition--_______________________.. 2 4Fuze setters:
Basic periodic tests -------___________. 126 84Use -------------------------------. 59,60 38
Fuzes (direct fire) _-_____________________. 78 46
Gunner's quadrant (basic periodic tests) _____ 121-125 82Gunners, tests for qualification:
Direct laying (T150E1 telescope)______ - 159-163 105Displacement correction_______________ 169-173 111Indirect laying, deflection only-_________ 164-168 107Laying for elevation:
Elevation counter -_______________ 179-183 115Gunner's quadrant--____-- __----- _ 184-188 116
Materiel ---------------------------- 204-208 123
132 AGO 2790C
Paragraphs PageGunners, tests for qualification-Continued
Measuring:Deflection ----------------------. 174-178 113Elevation ___________--_--------- 189-193 117Site to mask _------------------- 194-198 118
Outline of tests_---_------------------ 158 104Purpose and scope _____-------------- 151 102Standards of precision ______--------- - 152 102Test and adjustment of sighting and 199-203 120
fire control equipment.
Hand signals-._l_ ____.----------. 108 69
In battery, definition --------------------- 2 4Individual duties:
March order ____-------------------- 17 20Prepare for action__ ------------------ 16 19
Inspection, duties:After operation (march) -------------- 131 86Before operation (march) __----------- 131 86During halt --_---------------------. 131 86
Instructions, section drill _____------------ 8 10Laying:
Direct, firing by:Ammunition and fuzes------------ 78 46Field of fire ___-----------------. 76 45General------------------------- 74 44Individual duties during firing--_____ 83-97 53Priority of targets---------------- 77 45Range card_____----------.------ 75 44Trajectories--------------------- 79 48Vertical displacement table________. 80 50
Indirect, firing by:Detailed description of individual
duties:Chief of section--------------. 22-36 23Driver ______--------------- 72,73 43Gunner _______---- __-------. 38-46 29
AGO 2790C 133
Paragraphs PageLaying-Continued
Indirect, firing by-ContinuedNo. 1 --------------------. 48-53 35No. 2_______________________. 55, 56 37No. 3______________________. 58-61 38No. 4_______________________. 63-65 41No. 5 ------_---------------. 67-70 42
General duties of individuals_______ 20 21Precision____________________________ 98 59
Lights, aiming post_______________________ 100 60
Maintenance and inspections:Assembly, adjustments, and disassembly_ 128 85General …__________…--______________ 127 85Piece ______________________________. 130, 131 86Records_____________________________ 129 85
Measuring:Distance from piece to aiming posts_____ 100 60Site to mask …-___________-__________ 23 23
Minimum training schedule _______________ 150 102
Objective, training -_____________________. 145 96
Parallax______________________________ -- 116 80Performance characteristics, motor carriage_. 3 5Plumb line---------_____________________. 110 70Precision in laying _______________________ 98 59Preparation of range card ---------________ 75 44Preparing the piece for:
Firing _____________________________. 16 19Traveling--__-______________________. 17, 18 20
Qualification scores, gunners tests---_--____. 157 104
Range card, preparation --_________________ 75 44Reference lines, vertical ______-- _ ________ 102 62References ----------------------------__ 4, app 5
Safety precautions:Ammunition_---_--_--_-------------- 141 93
134 AGO 2790C
Paragraphs Page
Safety precautions-ContinuedDrill and firing _____________--------.. 143 95General___ _------------------------. 140 93Misfires--------------.-------------- 142 94
Schedule, minimum training --------------- 150 102Section:
Composition ------------------------- 5 8Data board -------------------------- 107 69Drill:
Change posts--------------------- 11 16Dismount ------------------------ 13 17Fall in ------------------------- 9 11Fall out ------------------------- 14 17Form the section __-------------- . 9 11Instructions ---------------------- 8 10Mount -------------------------. 12 16Objective ____-------------------- 7 10Posts---------------------------. 10 13
Signals, hand --------------------------- 108 69
Tables:I. Duties in preparing for action __--- 16 19
II. Duties in preparing for traveling__. 17 20III. Duties in firing ___________.----- 19 21IV. Vertical displacement ------------. 80 50V. Duties in maintenance and inspec- 131 86
tion (B) before operation (D)during halt.
VI. Duties in inspection and mainte- 131 86nance after operation.
Terms and definitions -------------------- 2 4Testing target -----------------.---------- 102 62Test (s):
Basic periodic ----------------------- 116-126 80Fuze setters-------------------------. 126 84Qualification of gunners:
Assistance ----------------------- 153 103Outline of tests------------------- 158 104Preparation --------------------. 156 104
AGO 2790C 135
Paragraphs PageTest(s) -Continued
Qualification of gunners-ContinuedQualification scores -----_-------- 157 104Scoring ________________________. 155 103Standards of precision …___________. 152 102Time -_________________________. 152 102
Synchronization, elevation counter______ 119 81Telescope:
Mount _________________________. 117, 118 81Panoramic T149E1 ------------- _ 120 82
Training:Conduct-------______________________ 146 96Individual periods ___________________ 149 98Objectives ______________________---- 145 96Purpose and scope --__________________ 144 96Schedule, minimum---------__________ 150 102Standards --_________________________ 147 97
Unloading the piece ______________________- 105 66
Vertical reference lines -__________________ 102 62
136 AGO 2790C
[AG 472.2 (4 Oct 56)]
By Order of Wilber M. Brucker, Secretary of the Army:
MAXWELL D. TAYLOR,General, United States Army,
Official: Chief of Staff.JOHN A. KLEIN,
Major General, United States Army,The Adjutant General.
Distribution:
Active Army:
Tee Svc, DA (1) Gen & Br Svc Sch (2) except ArtyTec Svc Bd (2) & GM Sch (50)Hq CONARC (18) Ord PG (2)Army AA Comd (2) Units org under fol TOE:OS Maj Comd (2) 6-315C, Armd FA Bn, 105-mmOS Base Comd (5) How, Self-Propelled (2)Log Comd (2) 6-316C, Hq&Hq Btry, Armd FAMDW (2) Bn, 105-mm How, Self-propelledArmies (2) (5)Corps (2) 6-317C, Armed FA Btry, 105-mmFA Gp (1) How, Self-propelled or How Co,USMA (3) Armd Cav Recon Bn (25)
NG: State AG (6); units--same as Active Army except allowanceis one copy per unit.
USAR: Same as Active Army except allowance is one copy per unit.For explanation of abbreviations used, see SR 320-50-1.
U. S. GOVERNMENT PRINTING OFFICE: 1956-400529
AGO 2790C 137
