Firearms Analysis Section

cartridge

unfired ammunition that has four componets: bullet, gunpowder, case and primer

bullet

the projectile that travels through and out of the barrel of a firearm

case

the case containing the primer, gunpowder and bullet

primer

the explosive composition in the base if the case, that when struck, ignites the gunpowder

handgun

a pistol or revolver

rifle

a long barreled rifled firearm usally ment to be fired with two hands from the shoulder

shotgun

a long barreled unrifled firearm usally ment to be fired with two hands from the shoulder

semi-automatic

a firearm that discharges a bullet, ejects a case, and with each depression of the trigger

automatic

a firearm that discharges a bullet, ejects the case, and feeds a new cartridge continuously for as long as the trigger is depressed.

breech face

metal of the firearm side, bolt, or frame around the firing pin hole

rifling

a series of lands and grooves twisting left or right that has either been cut or formed in the barrel of a firearm by the manufacturer

chamber

area at the beginning of the barrel or in a cylinder that holds a cartridge before it is fired.

extractor

metal hook that pulls the fired case out of the chamber

ejector

metal rod that knocks the fired case out of the firearm

comparison microscope

two microscopes optically bridged to one eye piece so to see two items of evidence side by side

rim fire

the cartridge has primer around the periphery of the base

center fire

the cartridge contains primer in the center of the base

gauge

refers to the diameter of a barrel of a shotgun

caliber

the diameter od the bore measured in decimal inch or millimeters

firing pin

a metal rod that strikes the cartridge primer to detonate the powder

single action

the hammer must be manually cocked before pulling the trigger

double action

pulling the trigger both cocks the hammer and fires the gun

action

the part of the firearm that loads and ejects the cartridge

choke

a constriction of a shotgun bore at the muzzle that determains the pattern of the fire shot

magazine

a device for storing cartridges

muzzle

the end of the barrel out of which the bullet exits.

round

-casing
-primer
-gunpowder
-bullet

shot

the small BB´s that are fired from shotguns
the gauge is the number of shot that are equal to a pound

slug

a single large projectile fired from a shotgun

bore

inside of the barrel

broach cutter

a metbod of rifling that grooves are cut out of the barrel wih three sets of steal rings

button

a method of rifling where a high pressure hard steel plug is forced through the barrel, it compresses the metal creating grooves

mandrel

a method of rifling where a hardened steel rod is placed into the barrel. The barrel is hammered to take the shape of the mandrel. Produces polygonal rifling

general rifling characteristcs

class-
caliber, direction of grooves, number of grooves, width of grooves

indivisual-
striations in the grooves of the bullet produced by the lands

casing characteristics

class-
caliber, brand

indivisual-
bolt face impressions, firing pin impressions, ejector mark, extractor mark