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Basic Gun Diagram Types of Firearms O Shotgun: Smoothbore Gun Designed Mostly to Shoot Lead Pellets of Varying Sizes

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Basic Gun Diagram Types of Firearms O Shotgun: Smoothbore Gun Designed Mostly to Shoot Lead Pellets of Varying Sizes Basic Gun Diagram Types of Firearms o Shotgun: Smoothbore gun designed mostly to shoot lead pellets of varying sizes o Rifle: A firearm having rifling in the bore and designed to be fired from the shoulder Types of Firearms (cont…) o Handguns: o Revolver: A firearm, usually a handgun, with a cylinder having several chambers so arranged as to rotate around an axis and be discharged successively by the same firing mechanism. o Semi-automatic Pistol: A repeating firearm requiring a separate pull of the trigger for each shot fired, and which uses the energy of discharge to perform a portion of the operating or firing cycle Ammunition Ammunition consists of four components: o Propellant o Projectile o Cartridge case o Primer o Self-contained ammunition, in which the propellant, projectile, and primer are held together by a cartridge case, is called fixed ammunition Ammunition bsapp.com bsapp.com bsapp.com bsapp.com Caliber of the Cartridge Caliber is a measure the diameter of the cartridge in hundredths of an inch. Common calibers include .22, .25, .357, .38, .44, and .45. Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong? Forensic Science: Fundamentals & 10 Investigations, Chapter 17 The Width of a Bullet determines Its Caliber Cartridge Cases The modern cartridge case serves several important functions: Contains the other components (projectile, primer, propellant) in a single unit for convenience of handling and loading Resists the firing-pin blow during ignition Forms a gas seal (obturation) Cartridge Case Identification Like bullets, cartridge cases can be identified as having been fired by a specific firearm. Cartridge cases like those on the right are mostly made of brass but can also be made of other materials. Cartridge cases come in a variety of finishes but all are made of a material that is softer than the materials found in a firearm. Any surface of the cartridge case that meets the inner workings of the firearm may be marked. Cartridge Case Identification Like bullets, cartridge cases can be identified as having been fired by a specific firearm. Cartridge cases like those on the right are mostly made of brass but can also be made of other materials. Cartridge cases come in a variety of finishes but all are made of a material that is softer than the materials found in a firearm. Any surface of the cartridge case that meets the inner workings of the firearm may be marked. Bullet Design “Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired Bullets vary in shape and composition There exist hundreds of different types of bullets Most types are variations on three main shapes & three basic compositions bsapp.com Three Main Shapes bsapp.com Round Nose Maximum penetration Cheapest shape to manufacture Easily loads into chambers bsapp.com Hollow Point Spreads or mushrooms on impact Causes additional damage to target Inhibits penetration bsapp.com Wad Cutter Used exclusively as a practice load Minimizes penetration Rips a hole in target paper which is visible by the shooter bsapp.com Three Basic Compositions of Bullets Lead ½ Jacketed Jacketed (Full metal jacket) bsapp.com Lead Cheap Dense Soft Easy to mold bsapp.com ½ Jacketed A lead bullet coated with copper half way up the exposed portion of the bullet Used primarily for hollow points Copper improves exit velocity Lead promotes mushrooming bsapp.com Jacketed A lead bullet completely coated in copper Copper improves exit velocity Used to hold the shape of the bullet in an effort to maximize penetration bsapp.com What happens to bullets when they are fired? bsapp.com Pull the Trigger and . 1.A pin or hammer strikes the primer. This causes a spark. 2.The powder is then ignited causing an explosion. 3.This explosion starts the bullet down the barrel of the gun bsapp.com Down the Barrel 4.As a bullet travels down the barrel of a gun it is twisted by the lands and groves of the barrel. bsapp.com Out of the Barrel 5.This rifling causes the bullet to exit the end of the barrel in a spiral motion. bsapp.com What happens to a bullet when it hits a target? •Most bullets tend to mushroom when they hit a target. •Some bullets nearly disintegrate. •Left are bullet fragments from a ½ jacketed hollow point. bsapp.com Some more bullets recovered after firing The striations from the rifling are still visible bsapp.com Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target. bsapp.com bsapp.com Examining Bullets: Rifling Rifling consists of grooves cut or formed in a spiral nature, lengthwise down the barrel of a firearm. A bullet is slightly larger in diameter than the bore diameter of the barrel in which it is designed to be fired. As a result, a rifled barrel will impress a negative impression of itself on the sides of the bullet like those seen b. Ballistics Striations bsapp.com bsapp.com bsapp.com bsapp.com bsapp.com Matching Procedure Fire bullets from a suspected weapon With the aid of a comparison microscope, compare these “test fires” to the suspected bullets Striations must be identical for a positive match bsapp.com Comparison Two scopes- Microscope One Field bsapp.com bsapp.com bsapp.com .
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