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Firearms Identification

Firearms Identification. Types, Function, ballistics and trajectory. Firearms identification. Includes: Comparison of bullets Operation of all types of weapons Restoration of obliterated serial numbers Detection of gunpowder residue on clothing and hands

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Firearms Identification

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  1. Firearms Identification Types, Function, ballistics and trajectory

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

  3. Bullet comparisons • 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

  4. Rifling characteristics

  5. Rifling Process • History of Rifling • https://www.youtube.com/watch?v=VbOt-y0oI68 • Present Day Method • https://www.youtube.com/watch?v=oALJDh43K3I

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

  7. Rifling Methods • Every manufacturer develops caliber specific rifling for optimal bullet performance • 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

  8. Rifling methods • 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

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

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

  11. Class vs. individual characteristics • 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

  12. Calvin Goddard (1891-1955) • Publishes “Forensic Ballistics” in 1925 • 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

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

  14. Bullet Design • Bullet design has everything to do with accuracy and trajectory

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