Firearms Identification Types Function ballistics and trajectory Firearms

Firearms Identification Types, Function, ballistics and trajectory

Firearms identification n Includes: Comparison of bullets n Operation of all types of weapons n Restoration of obliterated serial numbers n Detection of gunpowder residue on clothing and hands n Estimation of muzzle-to-target distances n

Bullet comparisons n n Rifling – the creation of spiral grooves on the inside of a gun barrel when it is drilled Bore – the interior of a gun barrel Lands – the raised parts of the barrel between the grooves Grooves – the cut out channels between the lands

Rifling characteristics

Rifling Process n n History of Rifling https: //www. youtube. com/watch? v=Vb. Oty 0 o. I 68 n n Present Day Method https: //www. youtube. com/watch? v=o. ALJDh 43 K 3 I

Rifling methods n Broach cutter – series of concentric steel rings, each slightly larger than the next n n simultaneously cuts all grooves in a barrel Rotates as it cuts, giving the appropriate direction (left or right) and rate of twist

Rifling Methods n Every manufacturer develops caliber specific rifling for optimal bullet performance n n n Rifles will have larger twist rates than pistols Rifles will have 1/12, 1/10, 1/8 Pistols will have similar rates of twist, however, the barrels are so short, the benefits are never realized

Rifling methods n n Button – a steel plug impressed with the desired number of grooves; no cutting involved – the button is forced under high pressure through the bore, compressing the surface Mandrel – similar to a button; inserted into oversized barrel, then barrel is hammered to acquire the impressions

Rifling examples: n n . 32 caliber Smith & Wesson revolvers 5 lands and grooves with a right-hand twist Colt. 32 revolver – 6 lands and grooves to the left 9 MM is 1/8”. 22 caliber is anywhere from 1/8”-1/16”

Bullet comparisons n n Caliber – the diameter of the bore of a rifled firearm; Expressed in hundredths of an inch or in millimeters

Class vs. individual characteristics n n n Each gun manufacturer chooses a rifling pattern, giving their guns a class characteristic Each gun barrel is bored and rifled, with minute differences, giving each firearm individual characteristics Even after hundreds of firings, bullets can still be matched to a unique gun

Calvin Goddard (1891 -1955) n Publishes “Forensic Ballistics” in 1925 n n n Discusses how bullets can be identified by their unique markings under a microscope. Became known nation wide for using these techniques to convict Sacco and Vanzetti FBI is pushed to adopt his practices

Ballistics n the science of projectiles and firearms. The study of the effects of bullets being fired from a gun. n Knowledge of chemistry, physics, trigonometry, and 3 D design are essential n As well as Mass, Velocity, and deceleration

Bullet Design n Bullet design has everything to do with accuracy and trajectory