Accuracy
The measure of precision in consistently obtaining a desired result. In shooting, the measure of a bullet's or gun's precision in grouping all shots close to the center of impact.

Action
The mechanism of a firearm by which it is loaded, locked, fired and unloaded. In a revolver, usually means the cylinder. In semi-automatic pistols it usually refers to the slide.  In rifles, refers to the bolt mechanism.

Assault Pistol
Technically a non-existent firearm. The military uses no pistols in an "assault" role as rifles are more appropriate. Even police swat teams do not use any kind of pistol as the primary firearm for the assault role.  A political contrivance that indicates a semi-automatic pistol with some unusual feature, such as a forward grip, a threaded barrel, or has a magazine other than in the pistol grip.

Assualt Weapon
As defined by the military; A select fire rifle firing a medium range cartridge configured for combat at short to intermediate ranges.   As defined by politicians and anti-gun groups; any military looking semi-automatic firearm that has a detachable magazine and has any one of; a pistol grip, detachable magazine, bayonet mount, collapsible or folding stock, flare launcher, grenade launcher, or flash hider. Credit for this term goes to Josh Sugarman of the Center to Prevent Handgun Violence who hoped to capitalize on the civilian population's ignorance in believing that this referred only to machine guns.

Automatic (weapon)
A (sub)machine gun. A firearm is said to be an "automatic weapon" if it is capable of firing more than one cartridge by pressing the trigger.  This is called "Fully Automatic" or "Full-Auto".  Modern firearms often have a select fire lever that allows firing in Full-Auto, Burst mode or Semi-Automatic modes. 

Ball
Early term for a bullet. Still used in firearms nomenclature for metal-enclosed round-nosed bullets.  Early bullets were round "balls" fired from rifles, muskets or handguns.  Still used today in blackpowder shooting.

Barrel
That part of a firearm the bullet passes through before exiting the firearm.

Blackpowder
Term denoting black gunpowder. Also used to denote firearms built to lower pressure specifications to use blackpowder instead of modern smokeless powders.

Bolt-Action
A firearm that uses a manually operated bolt to close the breech and fire the cartridge. Commonly seen on most hunting rifles.

Bore
The inside of the barrel of a gun of any kind and, in rifled arms, the diameter of the barrel before the rifling is cut. For shotguns, bore size is measured by gauge.

Brass
A term often applied to empty cartridge cases.  An alloy of copper and zinc of which cartridge cases are usually made.  Some cartridge cases are nickel plated "brass" for corrosion resistance.

Bullet
The missile only. Becomes a projectile when in flight. Not to be applied to the cartridge. See also ball.

Burst-Mode
The capability of firing a limited number of shots with a single press of the trigger. Where a full-automatic mode fires until the trigger is released, the burst mode stops firing after a predetermined number (3-4) of shots and the trigger must be depressed again to fire another "burst".

Caliber
Approximate bore or grove diameter expressed (in English) in decimals of an inch, otherwise in the metric system.  Frequently compounded to indicate powder charge; to show date of adoption; to show case length; or to show proprietor or designer. e.g. .30-40 Krag,  .30-06,  8x57mm,  .375 Holland & Holland, or .257 Roberts.

Cap & Ball
Meaning a percussion type firearm, most frequently a muzzle loading firearm, utilizing a percussion cap as a primer for the powder charge and a round ball as a bullet.

Cartridge
A complete unit of ammunition assembled. i.e. Case, propellant powder, primer and bullet. Usually applied only to rifle and handgun ammunition, but occasionally to shotgun shotshells.

Case
The paper, metal  or plastic container which holds all the other components of a round of ammunition. Sometimes called a "hull" or "shell" for shotguns or brass for other firearms.

Center Fire (CF)
Refers to centrally located primer in the base of metallic cartridges.  Most center fire cartridges are reloadable.

Chamber
That part of the bore, at the breech, formed to accept and support the cartridge.

Choke
A constriction at the muzzle of a shotgun barrel, designed to control or reduce the spreading and dispersion of the shot charge.

Clip
A metal device that holds a number of cartridges for fast loading into the magazine of a rifle or pistol. Clips are generally somewhat flat shaped, although the clip for the M1 Garand rifle is not.

Energy
The amount of work capable of being done by a projectile at a given range, expressed in foot-pounds. Found by multiplying the square of the velocity in FPS by the weight of the bullet in grains and dividing by 450,240.

FPS
Abbreviation for Feet-Per-Second. Also ft/sec, fps or f.p.s.

Foot-Pound
A unit of kinetic energy equal to the effort required to raise one pound to a height of one foot against normal gravitational force.

FMJ
Abbreviation for a Full Metal Jacket - a bullet with a fully enclosing metal jacket. See also metal case.

Full Metal Jacket
A type of bullet in which the core is completely encased in jacket material, except for a small opening on the bottom. Standard military bullet type. See also Metal Case.

Gauge
The measure of the size of a shotgun bore.  Gauge size indicates the number of pure lead balls required to weigh one pound which just fit the bore size.

Gilding Metal
A copper-zinc alloy used for bullet jackets.  Usually from 5% to 10% zinc, balance copper. Jackets are used to control expansion of expanding point bullets, such as soft point or hollow point bullets.

Grain
In weight measure 7000 grains equal one pound; 437.5 grains equal one ounce. May also be used in referring to a particle or kernel of powder.  However, "35 grains of powder" always refers to 35 of the weight-unit grains, never to 35 individual kernals of powder.

Grooves
Spiral cuts or impressions in the bore of a firearm which cause a bullet to spin as it moves through the barrel.

Group
The pattern made at the target of a number of shots fired with one aiming point and usually one sight setting.  Usually measured from center to center of the holes farthest from each other.

Half Jacket
A short jacket or bullet swaged with a short jacket which leaves some lead in contact with the bore. A three quarter jacket is similar, but longer, so the bearing surface of the bullet is covered by the jacket material.

Hangfire
Ignition in a cartridge which is delayed beyond the normal time after the firing pin has struck the primer.

Hollow Point (HP)
A bullet with a hollow cavity at the nose, designed to allow controlled expansion of the bullet upon impact. Jacketed hollow point bullets use a gilding jacket to further control expansion of the bullet and prevent fragments from forming.

IBS
International Benchrest Shooters

Jacket
The cover or skin of a bullet, usually made of gilding metal in the U.S.

Keyhole
The imprint of a bullet on a target which shows that the bullet was not traveling point-on at the time of impact.

Lands
The spiral raised portion of a bore remaining after the grooves have been cut or formed.

Machine Gun
A firearm which is capable of firing multiple shots with a single squeeze of the trigger. See also: Automatic weapon, Burst-Mode or Semi-Automatic.

Magazine
That portion of a firearm which holds the cartridges in preparation for the bolt, slide or mechanism to feed a cartridge from the magazine into the chamber.  Magazines may be "fixed" as an internal portion of the firearm or removable.

Magnum
A load or cartridge having greater power. A magnum case is usually slightly longer. e.g. the .44 Magnum is about one eighth of an inch longer than the .44 Special.  Or it may be a caliber with exceptionally larger powder capacity in relation to the bore diameter. e.g. the .264 Winchester Magnum.

Meplat
The diameter of the flat or blunt end of the nose of a bullet.

Metal Case (MC)
Sometimes called a Full Patched (FP) or Full Metal Jacket (FMJ) bullet. A type of bullet in which the core is completely encased in jacket material, except for a small opening on the bottom. Standard military bullet type.

Misfire
Complete failure of a cartridge to fire after the primer is struck by the firing pin.

Mushroom
The ability or capacity of a bullet to expand on or after impact. The name comes from the desired shape after expansion.

Muzzle
The front end of the barrel. The point at which a projectile leaves the barrel.

Muzzle Blast
The blast of the hot powder gasses from the muzzle of the gun with the attendant flash and noise.

Muzzle Energy (ME)
The energy of a bullet at the muzzle.  See also Energy.

Muzzle Loading
A firearm which is loaded from the muzzle end.  A firearm which does not use a metallic, paper or plastic cartridge to contain the powder and bullet.  Ignition is generally through the use of a percussion cap.  See also Cap & Ball.

Muzzle Pressure
The gas pressure in the barrel at the muzzle at the instant the bullet leaves the barrel.

Muzzle Velocity (MV)
See Velocity.

NBRSA
National Bench Rest Shooters Association

NSSF
National Shooting Sports Foundation.

Ogive
The curved portion of a bullet ahead of the cylindrical or shank section. Also the radius of this curve, usually expressed in calibers.

Patched (or Paper Patched) Bullet
A bullet commonly used in older black powder cartridges with a wrapped paper "patch". Derived from the even older "patch" used to wrap a muzzle-loading ball. The "patch" helped seal the powder gasses and reduced bore leading.

Pattern
The way a shotgun places its shot load. Generally measured as the percentage of a full shot charge that is placed inside a 30" circle at 40 yards.

Percussion
The type of ignition system used in some black powder firearms where a hammer or striker impacts a percussion cap which ignites the powder charge. See also Cap and Ball.

Pistol
A semi-automatic handgun.

Plinking
Shooting for fun without formal target shooting rules. e.g. shooting tin cans.
Note: Glass should never be used for plinking since it is difficult to clean up the area and glass does not biodegrade over time.

Powder
The propellant material used in firearms. Divided into two basic types; "smokeless" powder and "Black powder" or "Gunpowder".  It is produced in a wide variety of types, forms and brands. Variations are chiefly according to burning speed. Most "smokeless" powder contains a major percentage of nitrocellulose with small traces of other compounds intended to control the burn rate or prevent deterioration.

Primer
Also called "cap", deriving from "percussion cap" which is the priming form used with some muzzle loading arms.  In a centerfire cartridge the small metal cup containing a detonating mixture is used to ignite the propellant powder.

Projectile
A bullet or any other object projected by force and continuing in motion by its own inertia. A bullet is not a projectile until it is in motion.

Pyrodex
A modern, commercially made substitute for black powder that is cleaner burning,  more consistent and economical than black powder.

Recoil
The backward thrust or "kick" of a gun caused by the reaction to the powder gases pushing the bullet through the bore and the jet effect of the gasses themselves.

Revolver
A handgun which has a rotating cylinder that revolves when operated to fire a cartridge.

Rifling
Parallel spiral grooves cut or impressed into the bore of rifles and pistols in order to make the bullets spin, insuring steady, point on flight to the target.

RIMFIRE (RF)
Cartridges which contain the priming mixture within the rim. The most common example is the .22 rimfire cartridge.

Round
A military term meaning one complete cartridge.

Round Nose
A bullet design feature. Blunt, spherical nose shape. Typically a round nosed bullet made from lead (or more correctly, a lead, tin and antimony alloy).

SAAMI
The Small Arms and Ammunition Manufacturers Institute

Semi Automatic
A firearm that fires one cartridge (and only one cartridge) each time the trigger is pressed. Semi-Automatic firearms eject the empty cartridge, cock the hammer or striker, load a fresh cartridge from the magazine, chamber the cartridge and lock the breech automatically.

Semi-Wadcutter
A bullet design similar to a wadcutter, except that the leading end of the bullet is shaped into a slightly tapered blunt-end projecting further than the end of the cartridge case.

Shock
The effect of the transference of a bullet's kinetic energy to animal tissue or other target. Also what gun-owners suffer when they see the latest prices for firearms, ammunition, registration fees, etc.

Shot
The lead alloy spheres, sometimes copper or nickel plated which are used for the projectiles in smooth-bore guns.

Shotshell
A cartridge for a shotgun which contains the powder, primer, shot and the wad used to contain the shot. Modern shells are made from plastic with a brass base, with older shells made of a brass base and paper.

Sighting In
Firing a rifle or pistol to determine its point of impact at a specified range and to adjust the sights so the point of impact matches the sights.

Slide
The portion of a semi-automatic pistol which encloses chamber and slides rearward when a cartridge is fired.

Slug
A cup shaped, hollow base projectile, usually bearing external pre-cut rifling, intended for adapting shotguns to the hunting of larger game, such as deer.

Smokeless (Powder)
See Powder

Soft Point (SP)
Bullet design feature. Where a portion of the lead alloy core is exposed at the point or nose of a jacketed bullet.

Spire Point
A conically pointed bullet.

Spitzer
Bullet design feature. A bullet with a pointed nose.

Target Pistol
A pistol purpose-built for shooting targets accurately such as this Hammerli 280 model show at right.  Used in Olympic competitions and sporting matches.

Twist
The angle of the rifling in relation to the axis of the bore. Usually measured by length of barrel required to make one complete turn.

Velocity
The speed at which a projectile travels. Usually measured in feet per second (fps) at a given range.

Wad
A disc of paper, felt, cork, plastic or other material used for various purposes, primarily in shotshells, but occasionally in rifle or pistol cartridges.

Wadcutter
A cylindrical shaped shouldered bullet designed to cut a clean round hole in a paper target.

WCF
Winchester Center Fire

Zero
More correctly, "Zero Sight Adjustment". That adjustment of a gun's sights that will place an aimed shot at the desired point of impact at a given range.