2 - Firearm and Tool Mark Examination

• Automatic

• Semiautomatic

Type of Modern Firearms:

• Revolver

• Semiautomatic Pistols

Handguns:

Revolvers

The cartridges are held in firing chambers in a rotating cylinder.

Semiautomatic Pistols

Also called as autoloaders or self-loaders.

Gun Parts:

Lever and Slide Action Magazine Repeaters

Rifles:

Bolt-Action Magazine Repeaters

Rifles:

Single Shot Rifles

Loaded one at a time;

• there’s no magazine.

Semiautomatic Rifles

Squeezing the trigger fires one round

• Slide and Lever Action

• Double – Barreled

• Bolt-Action

• Single Shot

• Semiautomatic Shotguns

Shotguns: (4)

Slide and Lever Action

Loaded and cocked by pumping a slide or lowering and raising a lever

• The shot shells are loaded into tubular magazines under the barrel

Double – Barreled shotguns

Available in two configurations: over/under shotguns, in which the two barrels are aligned one above the other, and side-by-side shotguns.

• Break open to eject fired shotshells and each barrel is loaded separately

Bolt action shotguns

use the turn-bolt action

Single shot shotguns

may use rolling block or break-open actions

Automatic Weapons

Weapons that will continue to fire as long as the trigger is depressed and ammunition is available.

• Machine Guns

• Automatic rifles

• Submachine Guns

• Assault Rifles

Automatic Weapons: (4)

Machine Guns

These are military weapons that fire from a mount or have a bipod attached to the barrel to support the weapon when it is fired.

• Also mounted on vehicles or aircraft

Automatic rifles

Light machine guns

that feed ammunition from detachable box or drum magazine.

Submachine Guns

fire pistols ammunition

fed from detachable drum or box magazines.

Assault Rifles

fire a reduce charge rifle cartridge.

• First developed by Germans during WWII

Firearm Ammunition

Bullets may be lead, lead-alloy, semi-jacketed. Or full-metal jacketed.

Lead bullets

Soft and readily deformable.

Because lead is a ductile and malleable metal, lead bullets are easily marked by the rifling

Lead-alloys bullets

Contain a small percentage of an alloying element,

such as antimony in commercially manufactured bullets or tin in home-made bullets.

• Harder than lead bullets and are consequently used in weapons having higher muzzle velocity

Semi-jacketed bullets

Commonly consists of a lead core covered with a thin jacket of brass.

• The brass typically covers the sides of a bullet, leaving the lead core exposed at the nose.

Full metal jacket bullets

Consist of a lead core covered with a brass jacket.

• Compression tool marks

• Sliding tool marks

• Cutting tool marks

Types of Tool Marks: (3)

Compression tool marks

Results when a tool is pressed into a softer material.

• Such marks often show the outline of the working surface of the tool

Sliding tool marks

created when a tool slides along a surface;

such marks usually consist of pattern or parallel striations.

• Class characteristics are more difficult to determine from sliding tool marks.

Cutting tool marks

combination of compression and sliding tool marks

• cutting tool indents the material being cut

• and, as it does so, the working surfaces of the tool slide over the cut surface.