firearms and toolmarks Flashcards
what is a firearm
device (assembly of a barrel and action) from which a projectile is propelled by combustion
handguns
pistol
revolver
derringer
long guns
rifles
shotguns
pistol
handgun
a firearm designed to be held and fired with one hand
pistol
handgun in which the chamber is integral with the barrel
semi automatic pistol
handgun in which ammunition is fed by a magazine and the ammunition is fired and ejected with each pull of the trigger
derringer
generic term applied to many variations of ams one two or even four shot pistols
Henry deringer
revolver
firearm, usually handgun with a cylinder having several chambers so arranged as to rotate around an axis
discharged ammunition (cartridge cases) must be manually removed by the user
rifle
a long gun designed to be shot from the shoulder with a rifled bore
multiple different action types
semi automatic automatic and bolt
shotgun
a long gun designed to be shot from the shoulder typically having a smooth bore designed to fire shotshells
ammunition cartridge (live ammunition)
4 main components,
bullet/projectile
cartridge case
hols the components
propellant/powder
burns and produces pressure that propels bullet
primer ignites powder
parts of a cartridge
cartridge head
base of the cartridge case which contains the primer and location of the head stamp
headstamp
numeral letters and symbols stamped into the head of a cartridge case or shotshell to identify the manufacturer caliber gauge or other additional information
rimfire
primer contained In the rim around edges of head of cartridge case
centerfire
primer contained in the center of the head of the cartridge case
bullet types
full metal jacket (ball)
jacketed hollow point (JHP)
semi jacketed hollow point (SJHP)
lead hollow point (LHP)
semi-wad cutter (SWC)
wad cutter (WC)
range papers
caliber
for the firearm
approx diameter of the highest points of the inside of the barrel
typically expressed in hundredths of an inch or mm .354
for ammunition
numerical term without decimal point included in a cartridge designation to indicate the nominal (approx) bullet diameter, 38, 9mm
cartridge designation
term used to designate the specific cartridge for which a firearm is chambered
38 SPecial, 357 magnum
shotshell ammunition
hull/casing
projectile (shot or pellets)
wad column
powder
primer
guage instead of caliber
cycle of fire
loading (chambering)
locking
cocking
firing
unlocking
extraction
ejection
toolmark
created when two objects come into contact
harder object of two will leave a mark on softer object
in firearms, gun is tool
barrel leaves marks on bullet
breech fact, extractor, ejector, chamber, firing pin/aperture
two types of tool marks
striated
impressed
striated
marks (generally microscopic) on surface of an object caused by combination of force and motion where the motion of the tool is approx parallel to plane being marked
scratch
impressed
marks on surface of object caused by force where tool is approx perpendicular to the plane
stamp
bullet and barrel
barrels of pistols revolvers and rifles are typically rifled and contain general rifling characteristics
number width and direction of twist of the rifling grooves in a barrel of a given caliber firearm
land is raised groove is dent
as bullet travels down barrel the lands and grooves impart markings onto bullet
these are unique markings that are used to identify a particular firearm
class characteristics
diameter of bullet, caliber
number of lands and grooves
twist of
width of lands and grooves
areas that mark cartridge
extractor breech fact firing pin, firing pin aperture, ejector
unlocking begins after firing
unlocking continues as the pressure pushes slide rearward, while cartridge head slams back imparting marks on the softer material (breech face)
the rearward movement causes barrel to drop in
while still partially in chamber, cartridge case also drops down causing the shearing of the metal that has flowed into firing pin hole
softer metal cartridge case is being marked after firing by the breech face, firing pin, extractor, and ejector
