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
Present Day Method

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 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

13. 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

14. 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

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