Ballistics Notes - Allison Matias Firearms Tool Marks and...

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Allison Matias Firearms, Tool Marks, and Other Impressions bore The interior of a firearm barrel breechblock The rear part of a firearm barrel caliber The diameter of the bore of a rifled firearm, usually expressed in hundredths of an inch or millimeters—for example, .22 caliber and 9 mm choke An interior constriction placed at or near the muzzle end of a shotgun’s barrel to control shot dispersion distance determination The process of determining the distance between the firearm and a target, usually based on the distribution of powder patterns or the spread of a shot pattern ejector The mechanism in a firearm that throws the cartridge or fired case from the firearm extractor The mechanism in a firearm by which a cartridge or fired case is withdrawn from the chamber firearms identification A discipline mainly concerned with determining whether a bullet or cartridge was fired by a particular weapon gauge Size designation of a shotgun, originally the number of lead balls with the same diameter as the barrel that would make a pound. The only exception is the .410 shotgun, in which bore size is 0.41 inch Greiss test A chemical test used to develop patterns of gunpowder residues around bullet holes grooves The cut or low-lying portions between the lands in a rifled bore lands The raised portion between the grooves in a rifled bore rifling The spiral grooves formed in the bore of a firearm barrel that impart spin to the projectile when it is fired Individualization: frequently attainable in firearms and tool mark examination. -Structural variations and irregularities caused by: scratches, nicks, breaks, and wear permit the criminalist to relate a bullet to a gun. a scratch or abrasion mark to a single tool or a tire track to a particular automobile Bullet and Cartridge Comparisons Inner surface of the barrel of a gun leaves its markings on a bullet passing through it *these markings are peculiar to each gun*
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Gun Barrel- produced from a solid bar of steel that has been hollowed out by drilling.
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