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[email protected]

Tuning Guide

Hercules/Cummins B-3 RifleBy: R. Sauer & V. Palitang

Tuned B-3 featuring original stock finish and a Powerline 3-9x32 scope. Note that white spacer has been removed from the

butt.
mailto:[email protected]:[email protected]

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IndexCopywrite and contacts

R. Sauer V. Palitang

Introduction to the B-3 rifle

Introduction

Identifying the B-3 features

B-3 variants

Tuning options

Appearance options

Warnings

Tear down procedure

Introduction

Parts descriptions

Procedure

Basic Lube Tune

Introduction

Procedure

QF2 mainspring upgrade

Mainspring dimensions

B-3 Mainspring

QF2/B4 Mainspring

Mainspring pre-load and piston weighting

Leather seal expansion washer improvement

Introduction

Procedure

Mainspring bearing surfaces

Introduction

Procedure

Dimensions

Trigger polishing

Introduction

Procedure

Bed-liner stock coating

Introduction

Procedure

Making a muzzle brake for the B3

Introduction

Basic design

Procedure

All text and images contained within are the sole property of their authors. Reproduction and/or

modification in part or in whole is prohibited without specific written consent of the authors.

Questions or comments can be mailed to...

Russell S. [email protected]

Virgil S. Palitang [email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]

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Pre-tuned B3s and tuning services are available at

Introduction to the B-3 rifleThe B-3 is manufactured by Industry Brand of China and can often be found under the name of Cummins

and Hercules or simply called the B-3. It is an underlever rifle that is available in both .177 and .22 caliber.Typical velocity of the rifles out of the box is 450-500 in .22 and 550-600 in .177. Of course you may find

some that vary from this but quality control is not a strong point of the less expensive Chinese airguns. It is

simple rifle that is easy to work on, responds well to tuning, and is very accurate. The only complaints I havabout this rifle concern the trigger spring and cocking arm latch which are prone to breakage over time.

Identifying B-3 features

The following pictures illustrate some key areas that help to identify the B-3 rifle. The rifle featured below i

a late model variant with the cleaner woodgrain and finish and black mainspring guide. Note that the stockwas not relieved where the trigger guard is fitted as it is with the B-4 rifle. The rear sight it ahead of the

loading port and is spot welded to the receiver while the front sight is simply pinned to a turned-down sectioof the barrel.

B-3 front sight
http://webpages.charter.net/guru1/index.html

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B-3 rear sight

B-3 trigger (note that trigger is 2 piece sheetmetal unlike milled B-4 trigger)

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Typical late model B-3 grain pattern

Variants

You can basically break the B-3 into two categories, early model or late model. The late model rifles arepreferable as the finish and assembly tends to be better, there is less wood filler on the stocks, and the

improved spring guide is both stronger and shorter which allows for installation of a larger mainspring. It is

easily identified by the white spacer found between the stock and butt of the rifle and the spring guide istypically black as opposed to the early model which is white.

Tuning options

Some of the options that have been used in tuning the B-3 include basic cleaning and lubrication, leather seaimprovement, synthetic seal retrofit, B-4 spring upgrade, piston stroke modification, and transfer port tuning

I will try to touch on each of these as this guide progresses.Appearance options

There are many options when it comes to enhancing the looks of your B-3. Some modifications not onlyimprove it's looks but also improve other aspects of the rifle's performance. Some of these include shortenin

the barrel, installing a muzzle brake, shortening the cocking arm, refinishing or painting the stock, coating

the stock with bedliner (as was done in the example picture on the first page), and many more. You are onlylimited by your imagination. I will try to address the bedliner application and cocking arm modification late

in this guide.

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WarningsBefore getting into the steps involved I feel it may be best to cover a few thing that will help you avoid

trouble.

The trigger group on this rifle uses several pins as pivots for items like the sear, trigger, and anti-beartrap

mechanism. These pins are held in place by the stock so care must be taken during stock removal to avoidhaving these pins fall out. The best method for preventing this is to avoid having the rifle on it's side when

you remove the stock. I usually lay mine on it's back so that I have access to the underside and have found

that this works best.

1. The spring is under substantial load when installed in this rifle. Although I am able to remove thespring without a compressor, I would advise against it. A spring compressor should be used every

time you tear down your B-3 as it prevents damage to the rifle as well as yourself2. Moly (as in moly paste or lube) is harmful and should not be allowed to contact your skin. I suggest

using latex gloves to avoid this and make cleaning up easier.

3. ALWAYS hold the cocking arm when the chamber is open, ALWAYS have the stock installed when

testing the cocking action, and ALWAYS try to avoid having your hand between the cocking arm anthe barrel with the rifle cocked. It only takes on incident to hurt yourself badly and injuries can

include loss of limbs and broken bones so don't take these lightly.

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Tear down procedure

Introduction

There are several ways to go about tearing down the B-3 rifle but I have tried to lay this out in a way that wassist those who are doing this for the first time. As you gain experience with your B-3, you may find your

own way of doing things. Until then, this will help you get the job done.

I must assume that you have a spring compressor and some mechanical aptitude otherwise you wouldn't be

trying this. If you require a hospital visit after installing a light bulb, this probably isn't a great idea.

Parts

I am sure this will be overly simplified for many but it may prove useful to those who are just getting started

in this hobby.

1. Barrel-the portion of the rifle through which the pellet travels after firing2. Muzzle-the portion of the barrel where the pellet exits

3. Receiver-the portion of the rifle that the barrel attaches to, contains all internal parts

4. Cocking arm/lever-lever that you actuate to cock the rifle

5. Cocking link-connects the cocking arm/lever to the chamber

6. Chamber-the area where compression takes place, piston slides within7. Piston seal -seals piston to chamber in order to compress air, leather or synthetic

8. Piston -powered directly by mainspring, slides within chamber to compress air9. Mainspring-spring that drives piston forward upon firing

10.Spring guide -secures spring within receiver, stabilizes spring to avoid canting

11.Trigger-stamped steel lever that actuates firing12.Sear-locks piston in rearward position during cocking and releases piston during firing when actuate

by trigger

13.Trigger spring-connects trigger to sear14.Anti-bear trap-prevents trigger movement when cocking lever is in the fully cocked position

15.Expansion washer -found within leather piston seal, helps seal maintain shape and helps to secure it t

the piston16.Breach-portion of the barrel where the pellet is inserted17.Breach seal-seals chamber to the portion of the barrel where the pellet is inserted

18.Transfer port-orifice in chamber that air passes through before contacting pellet

19.Stock-the big wood thing20.Butt-your sitting on it

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1. With the rifle sitting on it's back, remove both front stock screws and the rear trigger guard screw

before removing the stock. Work slowly and watch for loose trigger pins.2. Remove trigger pins and set aside. The sear pin uses e-clips to retain it so carefully remove the e-clip

from one side of the pin and slide the pin out. Do not remove trigger spring from sear/springassembly. Doing so can cause premature spring failure and is not needed to service this rifle. Note:

the sear pin, sear, trigger, and trigger spring can remain in place during tear down if desired. Be sure

they are kept out of the way while servicing the remainder of the rifle.3. Remove the anti-bear trap spring assembly ( just ahead of the trigger group) by removing one

retaining screw. Leave screw in the spring retainer to keep the springs in place. The rest of the

mechanism can remain in place at this time. This step is optional since the cocking link can be

removed by extending the anti-bear trap springs and relieving pressure against the link.4. Unlatch the cocking arm and unscrew the pivot pin/front sling swivel. With the pivot pin removed,

rotate the cocking arm and link away from the barrel until it releases from the chamber. Once thecocking arm and link are removed, set aside the anti-bear trap.

5. Remove the plastic end cap at the rear of the receiver. Using a spring compressor, depress the spring

guide into the receiver and drive out the guide retaining pin. Slowly release spring tension with the

compressor.6. Remove the rifle from the compressor, the guide from the spring, spring from the piston, and then

slide the chamber/piston assembly out of the receiver.

7. Remove the piston from the chamber by pulling gently. Avoid catching the leather seal on the cockinslot in the chamber.

8. Remove the piston seal retaining screw and then the expansion washer from the seal

To reassemble the rifle, reverse the steps above making sure to apply blue threadlock to all screw threads,

especially the piston seal retaining screw. The illustrations above show the correct order of parts installation

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Basic lube tune

Introduction

The focus of this tune is to smooth the action of this rifle and gain a small amount of power in the process.Most of your time will be spent eliminating any areas within the action that might create excessive friction

between the moving parts. I will describe the process by breaking it down by individual parts. A thorough

cleaning should be done both before and after all polishing or sanding.

Procedure

1. ReceiverUsing sandpaper wrapped around a wooden dowel, smooth the inner surface of the tube. Pay close

attention to the areas that have been spot welded and the opening where the sear protrudes. Any area

that might catch on the chamber or piston needs to be smoothed.Also take a piece of sandpaper and round off the edges of the loading port to. Start with a course

paper ad work your way to a finer grit as you progress. Some minor sanding marks in the surface are

fine and will help to hold any lubricant in place. Also smooth the edges of the opening that the

cocking link enters.

Lubricate the interior of the receiver with a light film of moly paste being sure not to get any on thetrigger or sear. Do not lubricate the end of the receiver where the barrel enters.

2. ChamberUsing sandpaper, smooth out the front and rear edges on the outside of both ends. You want to

eliminate sharp edges that may gouge the inside of the receiver as it travels during cocking. Also

round off the edges of the opening that the cocking link hooks into.Using an automotive brake hone and a drill, hone the inside of the chamber until the surface is

uniform and as smooth as possible. If you plan on installing a synthetic seal, leave a slight crosshatch

If you are retaining the leather seal, get the surface as smooth as possible and then follow up with avery fine sand paper.

Lubricate the interior of the chamber with a very thin film of silicone grease (dielectric grease). Do

not lubricate the exterior.3. Piston

Using sandpaper, round off the front edges of the piston behind where the seal seats and the opening

that the spring enters. You want to be sure that the front edge of the piston will not gouge the chamb

as it travels forward during firing and that the rear will not gouge the receiver as it is cocked. Also usthe sandpaper to smooth out any weld marks and to soften the edges of the cocking groove. Polish th

indentation that the sear engages when cocked. Don't change the angle or shape of the indentation bu

simply smooth the surface. This will improve trigger feel.Lubricate the exterior of the piston with a light film of silicone grease. Do not apply grease to the

indentation that the sear engages.

4. Main spring

Use a fine stone or sandpaper to polish the spring ends. Also round off the cut edges of the end coilsto keep them from digging into the piston or spring guide. Inspect the spring for canting. If the sprin

has serious canting then it is best to replace it.

Lubricate the ends of the spring with a small amount of moly paste. If using spring tar, apply it lightlto the exterior of the coils except where you have applied the moly paste at the ends. If you aren't

using spring tar, apply a light film of moly paste to the exterior of all spring coils.

5. Spring guideRemove and molding seams from the guide where the end of the spring will seat. The spring should

be able to rotate as freely as possible on this surface.

Lubricate any guide surfaces that contact the spring with a light film of moly paste.

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6. Cocking linkSmooth all areas that contact the receiver or chamber using sandpaper. Do not alter the shape of the

hook that engages the chamber.

Apply a light film of moly paste on the portion of the cocking link that makes contact with the groovin the receiver.

7. Leather piston seal

Remove expansion washer and retaining screw from seal, degrease it using automotive brake clean opreferred cleaner, scuff exterior surfaces with sandpaper to raise a slight nap, then soak seal in leathe

conditioning oil for approx. 15 minutes. Once seal has been cleaned and soaked, knead the seal with

your fingers while adding oil as needed until it is pliable but not too soft. Once this is done dry the

seal using paper towels until it is just slightly moist to the touch.No further lubrication is needed.

8. Breach seal

Inspect this seal for cracks or other irregularities that may prevent it from sealing. If the seal is not ingood condition you will have to replace it. Replacing this seal is as simple as pulling out the old one

and pressing in the new one. Sometimes the old ones are rather hard and don't want to cooperate but

will come out. The QF2 cleaning kit contains 2 new seals that will fit this rifle. See the section onupgrading to the QF2 mainspring for more details on this kit.

No lubrication is needed.

9. Barrel

Use a length of nylon trimmer or weedwacker line to pull through a few cloth patches saturatedwith Goof off followed by dry patches. Repeat this until the patches come out of the barrel clean.

DO NOT USE bore brushes or metal cleaning rods or damage to rifling within the barrel may occur.

No lubrication is needed.

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QF2 mainspring upgrade

Introduction

Besides the basic lube tune, this has to be one of the better modifications you can perform on your B-3. TheQF2 spring is found in the QF2 cleaning kit that is available online from retailers like

www.southsummit.com. It not only includes the spring but also includes 2 breach seals, a new sear, and a

synthetic piston seal. The piston seal will need to be adapted if you wish to use it and the included oil and

cleaning rods shouldn't be used on any airgun you cherish. Those of you who have the late model version ofthe B-3 with the black spring guide have it easy. Those with the earlier white guide will have a little work

ahead of you.

Procedure

With the black spring guide, the QF2 spring is a perfect fit and requires no modifications. If you have thewhite guide, you will have to cut back the area of the guide where the spring seats until it matches the

dimensions above. The distance from the center of the retaining pin hole to the end of the spring seat must b

no longer than 1.640 inches. A little shorter is actually better as it allows more freedom for you to pre-loadthe spring on the piston end. The new spring should be lubricated as outlined in the Basic lube tune sectio

before installation.What to expect. Cocking effort will increase very slightly, velocity can increase anywhere from 50-100 fps

depending on your rifle, and the rifle will be much smoother to cock and fire. Installing the spring will take bit more effort as it is stronger and longer than the original so be sure that your spring compressor is up to th

task.

B-3 black guide with dimensions
http://www.southsummit.com/http://www.southsummit.com/

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Mainspring dimensions

For those who may be interested in finding alternative springs for the B-3, I have provided the specification

below. These dimensions are correct at the time of this writing. Due to production variations, your

dimensions may vary slightly from what is listed.

B-3 mainspring

Coils=36 Wire size=.117

Length=9.30

Inner diameter=.490

Outter diameter=.737

QF2/B4 mainspring

Coils=37

Wire size=.116

Length=10.25

Inner diameter=.484 Outter diameter=.734

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Mainspring pre-load and piston weighting

Pre-loading the mainspring is the act of inserting spacers between the spring and piston to decrease the

springs installed height. Adding pre-load can increase velocity and smooth out the rifle sometimes but it

needs to be done cautiously as it can also cause damage to the spring or prevent the rifle from cocking.People often use metal washers inside the piston where the spring seats to add pr-load and weight. Adding

weight can also add power sometimes but adding too much will cause piston slam. Piston slam is when the

momentum of the piston moving forward overcomes the resistance of the pellet in the barrel causing the end

of the piston to slam into the end of the chamber. This will send a shock through the spring and into theplastic guide and can cause them to fail. For those who wish to tune without adding much weight, inch

nylon faucet washers found in hardware or home improvement stores work nicely. Each washer is approx.

1/8 inch thick and adds little weight.

Three lubricated nylon washers installed in a B-3 piston.

I've found that an unmodified B-3 with the stock spring can usually run 3/8 inch of pre-load without bindingthe spring and often provides good results. If you want to try adding weight, pennies make a good testing

medium and can be used in conjunction with the faucet washers. Any washers or spacers that are installed

between the spring and piston should be lubricated with a small amount of moly paste.

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Leather seal expansion washer improvement

Introduction

Many people choose to keep the leather seal that the B-3 came with but wish it could seal a little better. Thimodification will improve the leather seals ability to do it's job and will make it's diameter adjustable so it

can be fitted to the chamber better.

Procedure

You will need two 3/8 inch faucet washers and one inch faucet washer. Remove the retaining screw and

original expansion washer from the seal. Remove the retaining screw from the expansion washer and theninstall the inch faucet washer followed by the two 3/8 inch faucet washers. Install the new assembly into

the seal, apply blue threadlock to the retaining screw threads, and install assembly onto the piston. The

tighter you turn the screw, the larger the mouth of the seal becomes. Adjust is so that there is a light amountof drag when the piston is moved within the cylinder.

Original expansion washer, modded expansion washer, leather seal

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Mainspring bearing surfaces

Introduction

Due to it's very nature, a coil spring will twist during compression and expansion. In most applications thisisn't much of an issue however, due to the length of the spring and the requirements we have for our airguns

this can present a problem when it comes to shooting. If spring twist is not controlled during the firing cycle

the rifle will produce substantial recoil which can effect accuracy. Since we can not eliminate this twisting

action we must learn to control it. The goal of this modification is to install lubricated bearing surfacesbetween the mainspring and the remainder of the airgun action. This allows the spring to rotate independent

in relation to the rest of the gun and may provide reduced recoil, higher velocity, and a quieter spring action

This procedure will add a minor amount of spring pre-load which must be taken into consideration in order avoid coil bind.

Procedure

You will need to find two metal washers, one for the piston end of the spring and the other for the guide end

Although I have been unable to find washers which fit without modification, adjusting their size is relatively

easy with a little mechanical inclination. The approximate washer dimension required are listed below.

Piston end

Thickness=.075Outter diameter=.790

Inner diameter= no specification required

Guide end

Thickness=.075

Outter diameter=.790

Inner diameter=.470

The piston end must have an external diameter that allows it to fit inside of the piston and rotate freely.Thickness and internal diameter on not important here however, thickness will effect mainspring pre-load.The guide end must have an internal diameter that allows it to slip over the guide shaft and rotate freely. The

external diameter must be small enough to allow it to fit within the receiver without interfering with normal

movement of the piston. The dimensions provided should work with most B-3 rifles. Once again, thethickness is only important in that it will effect spring pre-load.

Once you have the correct washer dimensions it is important that all surfaces be polished in order to reduce

friction. A fine sandpaper will handle this nicely.

With properly sized and polished washers, apply a slight amount of moly on both sides and install them in

their respective positions. Reinstall the mainspring and assemble rifle as normal. If, after assembly, the rifle

will not cock fully then you have either coil bound the spring or the rear guide is too large and is preventingthe piston from moving rearward enough to engage the sear. On an otherwise stock gun, coil bind should no

be an issue as it can use approx. 3/8 inch of pre-load safely.

Note that metal washers are not required if suitable synthetic versions can be found. Normally I would

suggest using synthetics at the piston end to avoid adding too much weight to the piston. When using

synthetic washers, it is best to use two washers back to back per spring end to keep friction to a minimum.Doing this increases our pre-load more than the other options but can produce excelent results. Treat

synthetic washers the same as metal ones as far as dimensions and lubrication are concerned.

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Black B-3 guide with lubed metal washer installed

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B-3 piston with lubed synthetic washers. Note that two are required when using synthetic washers.

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Trigger polishing

Introduction

Since composing the original version of this guide, I have received several requests to add a section on tunin

the B3 trigger. Well here it is.

Although this trigger group is extremely simple, care must be taken when performing any polishing in order

to avoid altering the surface angles where the sear and trigger blade make contact. Alteration of these anglescan cause a failure to cock or accidental discharge so pay attention!

Procedure

All polishing should follow the direction of component operation. In the following illustration that would be

left to right. Although a smooth surface is desired, do not sacrifice the surface angles to obtain one.

Following the illustration provided, polish both areas highlighted in yellow. After polishing, apply a thin film

of moly grease to the polished surfaces and trigger pins.Also note the area in red. This is the trigger spring which is prone to breakage. If you notice that the trigger

becomes "sloppy", it is in your best interest to examine this spring and probably replace it to avoid adangerous condition.

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Procedure

The only product I have tried so far has been the Dupli-Color brand of Truck Bed Coating. It has never give

me any problems and it is readily available so I have had no reason to try other brands. Based on this fact, I

can't speak for the results or techniques that might apply to other products. I would assume that the resultswould be the same with this technique but to do so is at your own risk.

Remove the stock from the rifle and then all hardware from the stock (butt, sling swivel, and trigger

guard) Degrease stock using Simple Green or comparable cleaner

Use 240 grit sandpaper or comparable to scuff the original finish.

Note that you do not need to strip the finish to bare wood, only to scuff the original finish sothat the bed-liner can adhere properly.

B4 stock which has been scuffed as mentioned above

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Using lint free cloth, dust entire surface of the stock

Shake can until mixing ball moves freely inside and make sure that the can is within 68-92 F.

In a well ventilated area, spray the bedding area from above the stock and then the openings beneath

the stock (trigger and cocking slot openings)

Be sure to seal entire bedding area

Move on to the exterior of the stock by spraying both the butt and fore-end

Now paint all remaining surfaces and blend into areas already covered.

distance between nozzle and stock should be kept at approx. 6 inches and spray motion shoulgo from end to end

Repeat the painting process 2-3 times allowing atleast 15 minutes drying time between coats

The more coats, the more aggressive the texture, the longer the final drying time

Allow the completed stock to dry for atleast 24 hours before reinstalling hardware and assembling thgun

This final drying time is important as it allows the finish to harden. If you do not allow it to

dry fully, it can be scratched.

The stock can be cleaned up with a damp cloth or you can also use furniture polish to maintain a

slight sheen

B-3 stock after bed-liner coating showing the protected bedding area

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This illustrates the bed-liner texture after applying 3 coats

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Making a muzzle brake for the B3

By Virgil S. Palitang

Introduction

The B3 - for all its charm - does come standard with something no air rifle deserves to be afflicted with. A

stamped iron front sight that is riveted and cross-pinned to a turned-down section of the muzzle. Out of the

box, my B3's front sight had a deformed hood, probably from sliding around unsecured in its box duringshipment. The iron sights worked, no question, but they were also the most hideous things I'd ever seen. So

when I came across a scope at the local sporting goods store, I figured it was time to get rid of the 'cancerou

mole' - the front sight.

After grinding down the rivets, punching out the retaining pin, and prying the front sight assembly loose, I

found that the turned down section of the muzzle was almost as ugly. It was mostly bare metal, but had

picked up some blueing in certain areas. There was even more of that wok oil in the small ridges of thissection. I suppose I should have cut it off, but then I would probably not be writing this article.

Basic design

Figure 1. Muzzle brake diagram. Not to scale

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Figure 1 shows the basic diagram of the muzzle brake assembly and also the parts that are involved. Itemize

list follows:

1/2 x 8 PVC pipe nipple

1.5 to 2 inches of 1/2 inch dia. hose

JB weld or similar

Small screw to be used as set screw

1/4 inch carriage bolt to be used in making the plug

Important note: The 1/2 inch hose sleeve is a modified piece of hose. It was originally labeled "RV water

hose" at the "mart of wal". This has 2 layers - a clear outer layer and a white inner sleeve. These layers are

separated by criss-crossed fiberglass threads. If you have seen it, you know what I'm talking about. It mightalso be marketed as 1/2 inch garden hose. The inner sleeve is what should be used. Discard the outer layer

and the glass threads.

Procedure

1. Prepare the muzzle. Make sure it is clean and free of oil or grease. Slip the hose sleeve onto the turned

down section as far as it will go. It will be a tight fit because the muzzle is a tad larger than 1/2 inch.

2. Prepare the muzzle brake body. Cut the threaded sections off of the PVC pipe nipple. Keep one of the cut

off sections. This will be the mold for the plug.

3. Slide the PVC piece onto the muzzle. The sleeve will make it a very tight fit. I sprayed a little WD-40 on

the sleeve to help slide it on. The WD-40 evaporates and the PVC piece stays put.

4. Making the plug.

Figure 2. Plug mold diagram. Not to scale.

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As it turns out, the head of a 1/4 inch carriage bolt fits inside a 1/2 inch PVC nipple. It's a bit loose, but not

much that it's unacceptable. The length of the carriage bolt isn't super critical as long as the smooth section imaking contact with the the JB weld. Drill a 1/4 inch hole in a wood block for the carriage bolt to go throug

Put a lump of JB weld in the mold and push the carriage bolt down to form it into shape. It might make

things easier if you polish the carriage bolt with auto wax before using it. I didn't, so it's not disastrous, but ihindsight, I think I should have waxed the bolt to make release a little easier.

5. Install the plug. It may take some persuasion, but once the JB weld has hardened, it can be removed from

the mold. This plug should now be installed into the muzzle brake body. It will probably look a little rough,but don't worry, JB weld is sandable.

6. Finishing. Once the plug is installed, drill into it and put in the set screw. I don't have access to any fancyscrews so I just countersunk a small metal screw into the plug. This keeps it in place while the face is sande

into an acceptable finish. I used a sanding block with 120 grit, then 220, then finished with 320. Use a 1/4

inch drill bit in the muzzle brake exit to widen the hole a bit, and adjust the hole if it seems off center. Paint

the entire assembly your choice of color. Black seems to work nicely, but if your personality/creativity callsfor something else, feel free to take this opportunity to express yourself.

That's all I have for now. As always, be safe and have fun!

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