Forensics Arson and Ballistics

Ballistics

Analysis of firearms and projectiles

Firearm

Weapon that expels projectiles by action of an explosive

Handguns

Can be used single handedly

Rifles

Fired from shoulder, Spiral grooved barrel makes bullet spin to improve accuracy 

Shotguns

Fire shells filled with pellets which spread in a circular pattern and reduce the need for accurate aim

Cartridge

case,primer, propellant, and projectile

Bullet

Projectile

Shell

case holding everything together

Primer

ignites propellant

Rim

Where extractor grips and removes casing once fired

Caliber

Diameter of cartridge

Compostion

brass, steel, plastic

Individual characteristics of a gun

Firing pen impression location on the base: whre the firing pen strikes the primer

Headstamps

Writing on the bottom of a bullet

Breechblock pattern

mark from when casing is forced back against the breechblock.

Extractor and ejector marks

This is from the mechanism that moves bullets into the firing chamber and push spent shells from the weapon

Rifiling

Spiral grooves in Barrell to make bullet spin

Grooves

Indents machined inside barrel

Lands

raised portion between grooves

Pitch

Angle of rifling

Twist

DIrection of spin

Class Characteristics of bullets

The number, width, debt, twist, and pitch of lands and grooves.

Individual characteristics of bullets

Strirations ( marks on the bullet from rifling)

Why Dont shotguns have rifling?

Multiple projectiles reduces need for spin/accuraccy. For comparison, the following are used:

extractor and ejector marks

primer dent mark

headstamps

Where is gunshot residue located typically?

The shooters thumb and back of their hand