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Ballistics
Vocabulary:
Action: The working mechanism of a firearm
Barrel: That part of a firearm through which a projectile travels under the pressure of powder gases. May be rifled or smooth.
Bore: THe interior of a barrel forward of the chamber.
Breech Face: The rear wall of the chamber which is against the head of the cartridge case during firing.
Breech Fack Markings: Negative impression of the breech face of the firearm found on the head of the cartridge case and/or primer after firing.
Bullet: A non spherical projectile for use in a rifled barrel.
Caliber: 1. Firearms: The approximate diameter of the circle formed by the tops of the lands of a rifled barrel.
2. Ammunition: A numerical term, without the dicimal point, included in a cartridge name to indicate the nominal bullet diameter.
Cartridge: A single unit of ammunition consisting of the case, primer, and propellant with one or more projectile(s).
Cartridge Case: The container for all the other components which comprise a cartridge.
Cartridge Case Head: The base of the cartridge case which contains the primer.
Chamber: The rear part of the barrel that has been formed to accept a specific cartridge.
Class Characteristics: Measurable features of a specimen which indicate a restricted group sourse. They result from design factors, and are therefore determined prior to manufacture.
Comparison Microscope: Essentially two microscopes connected to an optical bridge which allows the viewer to observe two ofjects simultaneously with the same degree of magnification. This instrument can have a monocular or binocular eyepiece.
Ejector: A portion of a fireaarm's mechanism which ejects or expels cartridges or cartridges cases from a firearm.
Extractor: A mechanism for withdrawing the cartridge or cartidge case from the chamber.
Firearm: An assembly of a barrel and action from which a projectile(s) is propelled by products of combustion.
Firearms ID: A discipline of forensic science which hasits primary concern to determine if a bullet, cartridge case or other ammunition component was fired by a particular firearm.
Groove: See RIFLING
Gunpowder: See PROPELLANT
Individual Characteristics: Marks produced by the random imperfections or erregularities of a barrel surfaces. These random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion or damage. They are uniqueto that barrel and distinguished between eachother.
Land: The raised portion between the grooves in a rifled bore.
Land and Groove Impression: The negative impression on the bearing surface of a bullet caused by the rifling in the barrel from which it was fired.
Pressure: In a firearm, the force developed by the expanding gases generated by the combustion of the propellant.
Primer: The ignition component of a cartridge.
Propellant: In a firearm, the chemical composition , which when ignited by a primer, generats gas. The gas propels the projectile(s). Also called GUNPOWDER
Rifling: Helical grooves formed in the bore of a firearm barrel during manufacture to impart rotary motion to a projectile passing through it.
Twist: The direction and rate of turn of the rifling, e.g., left hand, right hand.
Firearms tactical
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