An+Overview-AP

=Introduction to Ballistics=

WHAT ARE BALLISTICS?
- The study of bullets and fire arms

FIREARMS:
- A weapon such as a gun HOW DOES IT WORK? 1. You pull the trigger. The pin hits the base of the cartridge, making primer powder mixture. 2. There is a small explosion from the primer powder mixture that goes through the hole and then to the main gunpowder supply. 3. The main gun powder catches on fire and the pressure of the explosion pushes the bullet from he casing and into the barrel. The amount of gun poweder and the mass of the projectile in the cartridge determines how fast the bullet goes. 4. The bullet goes through the barrel and starts to spin before in leaves the barrel.

- Long Guns:

 * rifles: fire bullets
 * The bullets have a twisting action when they come out of the barrel
 * The barrel causes the bullets to have a certain ridge or raised area
 * These ridges helps ballistics identify the type of gun that was used
 * There are no identical barrels meaning no bullet will have the same markings making it easy for ballistic to match the gun where the bullet came from
 * shotguns: fire small round pellets

HAND GUNS:
- revolvers and semiautomatic - pistols: has a revolver to where it shoots many bullets - semiautomatic: fires one bullet when the trigger is pulled - fully automatic: fires bullets repeatedly when the trigger is pulled

GUN RESIDUE:
- When a firearm is fired they produce gunshot residue. - Residue are traces of smoke and particles from unburned powder. - Gunshot residue contains nitrates which sticks to a person who shot the firearm. - The residue decreases between the fire arm and increases on the victim. - In a crime scene investigators look at the persons hands who shot the firearm because there will be residue that was left on them. Chemical testing can determine weather or not who shot the gun even if they had tried to wash it off their hands.

FIREARM DATABASE:
- Used to search crime-scene evidence to registered weapons National Integrated Bullet Identification System - computer files of fire marks used in previous crimes