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Firearms Identification and Ballistics: Analyzing Bullets and Trajectories

This guide delves into firearm identification, bullet comparisons, rifling methods, and ballistics, covering history, restoration, and trajectory estimation. Learn about rifling processes, manufacturers' techniques, and famous forensic ballistics pioneers. Master the art of identifying bullets for individual firearms and understanding the intricacies of bullet design.

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Firearms Identification and Ballistics: Analyzing Bullets and Trajectories

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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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