Firearms and Ballistics Firearms: A Quick History
• Almost every gun is based on the same simple concept: You apply explosive pressure behind a projectile to launch it down a barrel.
• The earliest & simplest application of this idea is the cannon. The 1st handheld guns were essentially mini-cannons; you loaded some gunpowder & a steel ball & lit a fuse. • War typically resulted in the need for improved weapons technology. • In the late 1800’s, the revolver quickly became popular due to it’s size & quick loading. – It only had to be reloaded every 5-6 shots instead of after each shot. • Handguns reigned supreme for the past 200 years & to this day, remain the most popular & readily available firearm.
Firearms Identification
• Often confused with the term ballistics
• Ballistics is the study of a projectile in motion. – Inside the firearm – After it leaves the firearm – When it impacts the target Firearms Identification
Identification of Firearms is based upon this basic idea:
A harder object marks a softer one & imparts/transfers its microscopic irregularities to that object. Forensic Firearms Expert
• Did a suspect use this gun to kill that person? • Did these bullets come from that gun? • Was it really self-defense? • Is this a case of suicide, or is foul play involved? Forensic Firearms Expert
• Bullet Comparison • Weapons Function – Is it safe? Has it been modified? • Serial Number Restoration • Gunpowder Residue Detection – on clothes, hands, & wounds • Muzzle-to-Target Distances Pulling the Trigger
• Pulling the trigger releases the firing pin… • The firing pin strikes the primer… • The primer ignites the gun powder… • The powder generates gas that propels the bullet forward through the barrel & ejects the spent cartridge case.
What happens to a bullet when it hits a target? • Most bullets tend to mushroom when they hit a target.
• Some bullets nearly disintegrate. • Left are bullet fragments from a ½ jacketed hollow
point. bsapp.com Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target.
bsapp.com Some more bullets recovered after firing
The striations from the rifling are
still visible bsapp.com Caliber: the diameter of the gun barrel. • Caliber is recorded in – hundredths of an inch (.22 & .38) – millimeters (9mm) Anatomy of a Bullet Bullet Anatomy bsapp.com Shotguns
• Smooth barrel – Projectile NOT marked as it passes through • Fire small lead balls or pellets contained within a shell. • Characterized by: – diameter of the shot – size & shape of the wad – Gauge: diameter of the barrel • (ñ gauge ò diameter) Bullet Design • “Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired • Bullets vary in shape and composition • There exist hundreds of different types of bullets • Most types are variations on three main shapes & three basic
compositions bsapp.com Three Main Shapes
bsapp.com Round Nose • Maximum penetration • Cheapest shape to manufacture • Easily loads into chambers
bsapp.com Hollow Point • Spreads or mushrooms on impact • Causes additional damage to target • Inhibits penetration
bsapp.com Wad Cutter • Used exclusively as a practice load • Minimizes penetration • Rips a hole in target paper which is visible by the shooter
bsapp.com Three Basic Compositions of Bullets
• Lead • ½ Jacketed
• Jacketed (Full metal jacket) bsapp.com Lead
• Cheap • Dense • Soft • Easy to mold
bsapp.com ½ Jacketed • A lead bullet coated with copper half way up the exposed portion of the bullet
• Used primarily for hollow points • Copper improves exit velocity • Lead promotes mushrooming bsapp.com Jacketed • A lead bullet completely coated in copper