1. Firearms: Form, Function, and Physics

2. It is NEVER just the bullet

3. Ballistics Science of the travel of a projectile in flight
Internal ballistics
travel within the gun barrel
External ballistics
travel from gun muzzle to target
Terminal ballistics
path through the target
--- Wound Ballistics
motions and effects of a projectile in tissue
Trajectory: The path of a projectile through air

4. Basic Terminology Ammunition cartridges shot shell
Firearm ammunition comes in two forms: cartridges and shot shells.

5. Anatomy of a Cartridge Bullet/projectile Cartridge casing Gunpowder
Primer
contains shock-sensitive priming mixture, ignites propellant

6. Caliber Diameter of the bullet or barrel of weapon
Given in hundredth of an inch
Others measure the bullet, land or groove diameter of the barrel.

7. Typical Cartridge

8. Common Variations of Cartridges
Hollow Point
Soft Point
Full Metal Jacket
Total Metal Jacket
Black Talon
Armor-piercing
Case lengths
(short, long, magnum)

9. Hollow Point
Bullet with a cavity at the nose to aid in expansion at impact and decrease penetration and disrupt more tissue as it travels through the target.
Two interrelated purposes: to increase its size once within the target, thus maximizing tissue damage and blood loss or shock, and by remaining in the target to expend all of its kinetic energy in the target, some of which will be lost if the bullet continues through the target.

10. Soft Point Nose of bullet has exposed lead not covered by jacket
expands like hollow point when it strikes target
But slower expansion and greater penetration than hollow points

11. Full Metal Jacket Jacket covers all but the base of the bullet
Higher velocity of bullet
Less residue on bore (internal surface of barrel)
limited in their capacity to expand.

12. Total Metal Jacket
Jacket completely encases the bullet

13. Armor-piercing Designed to penetrate soft body armor
Has center post of hardened steel or bronze
Some coated with Teflon to minimize barrel wear when firing

14. Basic Terminology Rifling
“spiral” grooves cut into the bore of a barrel
. lands
. grooves
. bore diameter
Rifling patterns vary by manufacturer
Bore = internal surface of the barrel
Lands
the raised areas of the bore between grooves
Grooves
the lengthwise helix rifling (channels) in the bore
Bore diameter
interior diameter measured across the lands

15. Rifling
Benefits
the lands grip the bullet as it passes through the barrel and give it a rotary motion
has a gyroscopic effect that increases the stability of the bullet’s trajectory (flies like a well-thrown football)
greatly increased accuracy

16. Rifling Impressions left vs. right rotation conventional vs. polygonal
Rifling can rotate to the right or left
many types of rifling
conventional uses perpendicular cuts to form grooves, forming a sharp edge profile
polygonal rifling is characterized by grooves with rounded edge profile
conventional vs. polygonal

17. Firearm Types
Hand guns
Revolvers
Pistols
Long guns
Rifles
Shotguns

18. Revolvers

19. Pistols

20. Rifles Long barreled gun Rifled barrel Types single shot bolt action
pump action
self-loading

21. Rifles

22. Ammunition Types Rifle generally longer than hand gun cartridges
aerodynamic, pointed bullet
greater velocity
longer range

23. Firing a Gun The firing pin strikes the primer
The priming compound explodes producing a high temperature jet of flame that passes through the flash hole igniting the propellant
The propellant burns at a high speed and produces a large volume of gas

24. Firing a Gun Internal Pressure
when propellant burns, most of it turns into gas (CO2 and water vapor)
at first, gases are confined within the casing, and pressure is exerted equally on all surfaces (base & walls of cartridge and base of bullet)

25. Internal Pressure
once the bullet begins to move, the volume filled by the gases increases and the pressure begins to decrease
compensate by using moderated grains, increasing the rate of burning as the propellant is consumed
thus internal pressure does not drop so drastically once the bullet begins to move

26. Rifles vs. Handguns
Bullets fired from a rifle will have more energy than similar bullets fired from a handgun
more powder can be used in rifle cartridges
rifle bullet chambers are designed to withstand greater pressures (70,000 psi vs. 40,000 in handguns)

27. Rifles vs. Handguns Rifles are more accurate than hand guns
longer barrel increases distance over which the bullet accelerates
rifle bullets have greater velocity
longer barrel also allows more time to impart the gyroscopic spin, creating a faster spin and more stable flight