Glossary/ Frequently Asked Questions

This is my attempt at educating new shooters of the different firearm terminology in use. The FAQ is in its infancy right now, but I hope it will become a valuable tool for new shooters. If you find any errors, please correct me.

Glossary of firearms terms

ACP: Stands for Automatic Colt Pistol. Associated with cartridge names like .45ACP and .380ACP.

Action: The mechanism by which the firearm operates. Common actions include bolt and lever (such as used with rifles) pump action (often found on shotguns) and double and single action (used on pistols and revolvers)

Ball ammo: In modern usage, it means a fully jacketed bullet with a round or pointed nose.

Blowback: A semi or fully automatic action where the bolt does not lock. The breech is held closed by the weight of the bolt and the pressure provided by the recoil spring. Most often found in small pistols and in submachine guns like the Uzi and MP5.

BMG: Stands for Browning Machine Gun.

Bullet: The projectile in a piece of loaded ammunition. It is incorrect to use this term to mean the entire loaded cartridge.

Caliber: This is confusing to almost all new shooters. Basically, it is the diameter of the bullet, in inches. However, the name of the cartridge (like .357 magnum or .38 Special, which actually use bullets of the same diameter) does not necessarily denote the exact measurement of the bullet diameter.

Carbine: A rifle with a relatively short barrel. Typically this means 16" or less.

Choke: Restriction at the muzzle end of a shotgun that affects the shot pattern.

Clip: A small piece of metal used to hold ammunition. The firearm can be quickly loaded from this clip. Not to be used as a synonym for magazine.

Corto: Italian for short. 9mm Corto is the same as 9mm Kurz which is the same as .380ACP

Field strip: Disassembling a firearm only as far as needed to clean and lubricate it.

FMJ: Stands for Full Metal Jacket. A bullet that is jacketed with a metal coating, often copper.

Gas operation: A design common among semi and fully automatic guns, where propellant gas is diverted and used to drive a piston that cycles the action of the gun. Used on the AR-15/M-16 family of rifles.

Gauge: The bore size of a shotgun. It is defined by the number of lead balls of bore diameter that equal one pound. Therefore a 12 gauge bore means 12 lead balls of the same diameter as the bore weigh one pound.

Grain: A measure of weight, often used for bullets and powder charges. There are 7,000 grains in a pound.

JHP: Jacketed Hollow Point.

Magazine: An ammunition loading device that can either detach or be permanently mounted to the firearm. This is different from a clip.

Minute of Angle: An arc equal to 1/60th of a degree. It is used as a meansurement of accuracy. Conveniently enough, 1 MOA is equal to one inch at 100 yards. Half inch groups at 100 yards would equal .5 MOA accuracy.

Muzzle: The 'business end' of a gun. The front end of a barrel.

Muzzle energy: The energy of the bullet the moment it leaves the barrel. The weight of the bullet (in grains) times the velocity of the bullet squared (in feet per second) divided by 450130.33 equals energy in foot-pounds. In other words, Energy = (wt * V^2) / 450130.33

NICS: National Instant Check System. The [allegedly] instant check system used to verify the identity and legal status of gun purchasers.

OAL: Over All Length. The total length of a loaded ammunition cartridge, as measured from the tip of the bullet to the base of the case.

Parabellum: Latin term meaning "For war." Used in the cartridge name 9mm Parabellum, which is the common 9mm pistol round.

Plinking: Informal target shooting. One of the best ways to have fun with your guns.

QD: Abbreviation for quick detach.

SAAMI: The Sporting Arms and Ammunition Manufacturers Institute. Sets product standards for firearms and ammunition.

Wadcutter: A bullet with a completely flat nose, designed to cut clean holes in the target for competitive shooting.

Frequently Asked Questions

What does the second number in cartridges like 30-06, 30-30, and 7mm-08 mean?

When a new cartridge is designed, whoever created the cartridge gets to name it, this leads to a wide variety of naming conventions. In the case of these three cartridges, the second number means the following:

30-06: A .30 caliber bullet, adopted by the armed forces in 1906.

30-30: A .30 caliber bullet, fired with a 30 grain charge of smokeless powder.

7mm-08: A 7mm bullet in a necked-down .308 Winchester case.

What shotgun load should I use for home defense?

Ask a dozen shooters, you'll get a dozen answers. One of the main concerns is over penetration. If you live in an apartment, you may want to stick with #6-#9 birdshot. Where over penetration is not a concern, #4 buckshot or even slugs are used. One compromise is to load the first 2 rounds with birdshot, the rest buckshot. I strongly suggest against using special shotgun shells like flechette rounds, it may be used against you should your assailant or his next of kin decide to sue you.

Why should I join the NRA?

If you are a gun owner, you must understand that our rights are being eroded away day by day. As gun owners we must be politically active in preserving our rights. The best ways to do this are writing and calling your elected officials and joining groups like the NRA, GOA, and Second Amendment Foundation.