Firearms Flashcards
What are microscopes used for in firearms?
To analyze the different rifling and grooves left on a bullet.
automatic weapons/ fully automatic
continues to fire as long as its trigger is depressed and ammunition is available
semiautomatic weapons
fires and reloads itself before firing another shot; a self-loading weapon
Functions
blow-back
recoil
gas piston
Blow-back
fired cartridge blows back against the breechblock, forcing it to the rear and extracting and ejecting the expended cartridge casing
Recoil
the barrel of the weapon and its breechblock recoil a short distance together
Gas piston
gas forces piston to the rear; rod connects the piston to the breechblock so that the breechblock is also pushed to the rear
Hundguns- Revolver
Cartridges are held in firing chambers in a rotating cylinder
single action- fired by manually cocking the hammer and then pulling the trigger
Double action- fired by a long trigger pull that raises the hammer, indexes a firing chamber under the hammer, and then allows the hammer to drop, firing the cartridge
Double action
fired by a long trigger pull that raises the hammer, indexes a firing chamber under the hammer, and then allows the hammer to drop, firing the cartridge
Single action
fired by manually cocking the hammer and then pulling the trigger
Semiautomatic pistol (aka autoloaders or self-loaders)
- cartridge is chambered in the pistol; simultaneously the firing mechanism is cocked
- shooter pulls trigger, firing cartridge
- some energy produced by the fired cartridge is used to move the slide or breechblock to the rear
- spring compressed by the rearward travel of the slide or breechblock
Lever Action Rifle
Lever below the weapon’s receiver is dropped to move the breechblock to move the breechblock to the rear and cock the firing mechanism
Raising the lever chambers a fresh round
Pump action rifle
AKA- slide action
A slide under the barrel is moved to the rear to extract and eject the expended cartridge and cock the firing mechanism; pushing the slides forward chambers a fresh round
Bolt action
Expended cartridge is extracted and ejected by drawing the bolt to the rear; moving the bolt forward strips a fresh cartridge from a magazine and inserts it into the chamber
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world-leading trade fair for hunting, shooting sports, equipment for outdoor activities and for civilian and official security
land and groove rifling
raised portions of the rifling are the lands and the recessed portions are the grooves
polygonal rifling
hills and valleys
provides a better gas seal in relatively large diameter bores
produced by hammer forging the barrel around a mandrel containing reverse impression of the rifling
Gauges
the diameter of a shotgun’s bore. The gauge is calculated by determining how many lead balls of the same diameter as the bore would weigh one pound
smokeless powder
propellant composed of nitrocellulose (single-base) or nitrocellulose plus nitroglycerin (double-base powders)
black powder
the original gunpowder, composed of charcoal, saltpeter, and sulfur, now used chiefly in antique firearms and in fireworks
NIBIN
National integrated ballistic information network
national database of digital images of spent bullets and cartridge cases that were found at crime scenes or test fired from confiscated weapons
Bureau ATF manages the system and provides the equipment to crime labs around the country.
ATF Crime Lab
National firearms examiner academy in Beltsville, Maryland
Invetigators learn to match bullets to firearms, restore obscured or removed serial numbers, and to study crime scene reconstruction
Applying the scientific method
3 possible outcomes
- hypothesis is supported by the data indicating it is possible
- hypothesis is rejected and excluded as a possibility
- data is inconclusive
OSAC
Organization of Scientific Area Committees (OSAC)
Firearms and toolmarks subcommittee
