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INDEPTH ANALYSIS OF INTERNAL BALLISTICS

1C15 Firearms, Tool Marks and

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What is Ballistics?•The study of projectiles, trajectories, and

the effect on the target

What is Firearms Identification?

•A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon

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● Forensic Ballistics is divided into three categories:

– Internal ballistics

– External ballistics

– Terminal ballistics

THE THREE CATEGORIES OF BALLISTICS

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A Internal ballistics

What happens in the weaponB External ballistics

What happens after the bullet leaves the barrelC Terminal ballistics (wound ballistics)

What happens when the bullet hits the target

DESCRIPTION OF THE THREE CATEGORIES OF BALLISTICS

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4C15 Firearms, Tool Marks and

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WHAT’S A CARTRIDGE?A cartridge (also called a round or a shell) is a type of ammunition) which is is a combination of:

bullet casingbullet (projectile)propellant) (usually either smokeless powder) primer

All of which is precisely made to fit within the firing chamberof a firearm.

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5C15 Firearms, Tool Marks and

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Cartridges Design

The bullet, usually made of metal, is out front with the cartridge, holding the primer and propellant powders, behind.

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7C15 Firearms, Tool Marks and

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What Are The Three Types of Bullets?

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8C15 Firearms, Tool Marks and

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How a Gun Works 1. The firing pin hits the base of the cartridge,

igniting the primer powder.

2. The primer powder sparks through the flash hole to the main propellant supply.

3. The pressure of the explosion pushes the bullet from the case into the barrel.

4. The bullet follows the lands and grooves spiraling out of the barrel.

● http://www.youtube.com/watch?v=c1VD1D1hLsQ

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9C15 Firearms, Tool Marks and

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10C15 Firearms, Tool Marks and

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What is effect does rifling do to a bullet?

• Rifling is the process of making helical in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis.

• This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.

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11C15 Firearms, Tool Marks and

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•A BROACH CUTTER USED TO CREATE RIFLING IMPRESSIONS IN A BARREL

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12C15 Firearms, Tool Marks and

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As a result of rifling, a barrel will impress a negative impression of itself on the sides of the bullet

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13C15 Firearms, Tool Marks and

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Matching

impressions

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14C15 Firearms, Tool Marks and

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15C15 Firearms, Tool Marks and

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A Fired bullet: Class evidence

•Different gun manufacturers use different rifling techniques. These techniques impart the class characteristics on a fired bullet.• Number of impressions

• Width of impressions

• Depth of impressions

• Angle of impressions

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16C15 Firearms, Tool Marks and

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Q: How are these 2 guns different

A: caliber

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17C15 Firearms, Tool Marks and

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What is caliber?

• Caliber = the diameter of the bullet.

• Measured in hundredths of an inches.• .22, .357, or .50

• Measured in metrics• 9mm

Question: Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong?

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18C15 Firearms, Tool Marks and

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Showing variation within caliber

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19C15 Firearms, Tool Marks and

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Striations on bullets are not the only features used in firearm investigations.

• BREECH MARKS PLAY A VITAL ROLE IN DETERMINING IF A CERTAIN BULLET WAS FIRED FROM A FIREARM.

• BREECH MARKS ARE FOUND ON THE REAR OF A FIRED CARTRIDGE

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20C15 Firearms, Tool Marks and

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22C15 Firearms, Tool Marks and

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• When a bullet is fired, the explosion forces:

1. the bullet down barrel

2. the cartridge back against breech

– Leaving a negative impression on the back of the cartridge

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23C15 Firearms, Tool Marks and

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Depending on the make of gun & normal wear and tear, the breech markings will pick up class, and hopefully, individual characteristics.

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24C15 Firearms, Tool Marks and

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Examples of breech markings

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25C15 Firearms, Tool Marks and

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Shot Gun vs. Handgun

• Shotguns have smooth barrels with no rifling.

• Are there lands or groves on the bullet(s)?

• How can a F.S. identify trace evidence left by a shotgun?

• Only by marks on the spent shell casing(s):

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26C15 Firearms, Tool Marks and

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27C15 Firearms, Tool Marks and

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28C15 Firearms, Tool Marks and

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Shotgun into ballistics gel

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29C15 Firearms, Tool Marks and

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How CSI determines if a recovered bullet from a crime scene came from a suspected gun

• http://www.youtube.com/watch?v=3EJrbpg43qM

Disclaimer: this video is oooooold

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30C15 Firearms, Tool Marks and

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THE END

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31C15 Firearms, Tool Marks and

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