Firearms Glossary

caplock

(1) A muzzle-loading gun whose ignition system employs a percussion cap, a small, thimblelike metal cup containing a detonating mixture. This cap, placed on a "nipple," transmits flame to the powder charge when struck by the gun's hammer. (2) The lock mechanism itself.

barrel throat

(1) That part of a barrel between the chamber and rifling. (2) The funnel-shaped area comprising part of the feed ramp at the back of the chamber on some pistols. Example: Colt's government model.

face

(standing breech) The vertical part of the shotgun action body through which the firing pins normally protrude and against which the breech end of the barrel is fitted.

Enfield

A British military arsenal. For many years a generic term used to refer to a multitude of muzzle- and breechloading guns and several revolvers by that maker.

floating barrel

A barrel inletted in such a way that it never contacts the stock, even upon firing.

cross bolt

A bolt or pin passing laterally through the buttstock behind the recoil lug to strengthen the area and transfer recoil loads over a wide area of the stock.

blind magazine

A box magazine completely concealed within the stock.

dumdum bullet

A bullet designed by Capt. Bertie Clay, a British officer attached to the munitions works at Dum Dum, India, in the late 1800s. The dumdum bullet was a form of jacketed, soft-point, expanding bullet that produced terrible wounds. The dumdum bullet was prohibited by the Hague Convention in 1899.

controlled-expansion bullet

A bullet designed to expand freely and quickly at relatively low velocities and yet won't generally fragment when entering animal tissue at high velocity. This type of bullet ensures deep penetration without creating an abnormally large wound.

flat-point

A bullet shape having a blunt tip, used especially in rifles with tubular magazines.

cross-eyed stock

A buttstock that's bent or shaped to allow the shooter to mount the gun on one shoulder while viewing the sights with his or her opposite eye

everlasting case

A cartridge case made from heavy brass stock, intended for extended reloading life.

belted case

A cartridge case with a raised band or belt at the base. The belt strengthens and reinforces the case base, and headspaces the cartridge within the chamber.

express cartridge

A cartridge that uses abnormally light bullets for its caliber, which are fired at unusually high velocities. Not in general use today.

deburring tool

A chamfering-deburring device used to remove rough edges and metal burrs from the mouths of cartridge cases. Also provides a chamfer to assist in bullet seating.

compressed charge

A charge of gunpowder upon which the bullet is seated to the point of compressing the powder.

flake powder

A chip-type smokeless powder that usually burns rapidly.

CO2 (carbon dioxide)

A colorless, odorless, incombustible gas usually supplied in steel containers, used in modified air and tranquilizer guns.

cap box

A compartment usually found in the buttstock of a blackpowder rifle or shotgun for carrying caps.

cartridge

A complete round of ammunition, made up of a cartridge case, primer, bullet (or shot), and powder.

base wad

A compressed paper filler or plastic material at the rear of the powder charge and inside the head of a shotgun shell that forms part of the combustion chamber.

conidial bullet

A cone-shaped bullet.

chopper lump

A construction method for double-barreled shotguns in which a "lump" extends beneath the breech of the barrel to form an integral part of the barrel.

copper crusher

A copper alloy cylinder of known density and precise dimensions, used to measure chamber pressure in pounds per square inch

cartridge trap

A covered compartment, usually in the buttplate or underside of the buttstock, where spare cartridges are carried. Common in European sporting arms.

case trimmer

A cutter-type device used to remove excess material from a case mouth or neck.

cut shell

A cutting process to reduce shot dispersion. A hazardous practice of cutting the shotshell partially through, forward of the powder wad. The forward portion of the case separates, holding the shot together for a considerable distance after leaving the barrel.

bullet

A cylindrical projectile with a pointed, rounded, flat, or semiflat point. Usually made from lead alloy. Some bullets are covered, or partially covered, with a thin metal jacket. See ball.

cant

A deviation or leaning of the gun's vertical axis from the true vertical. If the shooter leans his or her gun to the right, it's said to be "canted right."

brass catcher

A device attached over the ejection port of a firearm to catch ejected brass. Usually used on shooting ranges during practice sessions.

flash hider

A device attached to the muzzle of a military arm to conceal the flash. Also called flash suppressor

adjustable choke

A device attached to the muzzle of a |shotgun that allows the shooter to change choke |degree rapidly. Some types employ tube inserts, others an adjustable collet.

doll's head

A device consisting of a top extension of the double shotgun barrel that's wedge-shaped and strengthens the action against the recoil's torque.

case remover

A device designed to grip and extract a ruptured case from the chamber. Also referred to as a case puller or case extractor.

Berdan decapping tool

A device for depriming Berdan cases.

bullet puller

A device for removing bullets from loaded cases.

firing-pin stop

A device for retaining a firing pin while allowing easy tool-less removal of same.

cutts compensator

A device for single-barreled shotguns that provides adjustable choking and also reduces recoil.

burst limiter

A device in a full-automatic weapon that allows for a specified number of shots to be fired with a single pull of the trigger, usually three.

disconnector (interruptor)

A device in autoloader arms to prevent more than one shot being fired by a single trigger pull. Usually functions by breaking the connection between trigger and sear as the breech opens, and reconnecting when breech closes fully.

compensator

A device placed on the muzzle of a firearm to reduce upward movement of the muzzle brought about by recoil forces during firing.

cocking indicator

A device that informs the shooter that the gun is cocked. A pin-type indicator is found on some hammerless shotguns and on pistols, while exposed cocking knobs are considered cocking indicators on bolt-action rifles.

case gauge

A device used to measure overall cartridge case length to determine if the neck needs trimming.

clip

A device, metal case, or reservoir designed to hold a number of cartridges, to permit their easy insertion into a fixed magazine. A slender metal strip from which cartridges are stripped into a magazine well. A clip isn't a box magazine (detachable or otherwise), and the two words clip and magazine should not be used interchangeably, although it's commonly done.

donut pattern

A donut-shaped shotgun pattern. The hole in the middle of the pattern is generally caused by the interference of the old-style top wad.

Farquharson rifle

A falling-block, single-shot rifle considered by many to be the epitome of traditional single-shot rifle development. Most often encountered in large calibers intended for large game.

automatic weapon (machine gun, submachine gun)

A firearm that will chamber, fire, and eject continuously until all of its ammunition is expended or the trigger is released.

cocked & locked

A firearm that's fully loaded (including the chamber) with the hammer cocked and manual safety engaged. Usually applies to a carry mode for single action, semiautomatic pistols

CO2 gun

A form of air gun that substitutes CO2 gas for compressed air as an energy source

falling block

A form of single-shot action where the breech block travels vertically in a mortise in the receiver. Generally, the block is lowered through the opening in the bottom of the receiver by a finger lever. Examples: Sharps and Winchester single-shot rifles.

crimp-on gas check

A gas check design that crimps or pinches on the base of a cast bullet and won't come off in the case or barrel or in flight. The gas check, a short brass cup, reduces leading and improves accuracy

Derringer

A generic term (note spelling with two r's) applied to many small, muzzle- or breech-loading, single or multibarreled pistols. Sometimes (incorrectly) spelled with one "r." Deringer pistols were made by Henry Deringer.

combination gun

A gun containing at least one shotgun barrel and one rifle barrel or a combination of two or more barrels with a possibility of differing calibers for each barrel. Generally, combination guns are of a break-open shotgun configuration with various caliber and gauge combinations. The most common are the twobarreled over-and-under rifle and shotgun combination and the German drilling, two shotgun barrels over a rifle barrel.

blowback

A gun malfunction generally caused by excess headspace or too-high chamber pressure. Such conditions cause the case to rupture, and powder gases escape into the action and possibly the shooter's hands and face.

American black walnut (American walnut)

A gun stock wood frequently used in North America, with an excellent strength/weight ratio and dense grain characteristics.

Dreyse, Johann Nikolas (1787-1867)

A gunsmith and manufacturer made famous by the development of the breech-loading system. Known as the father of the bolt-action rifle.

buttplate

A hard metal or plastic protective plate covering the wood of a rifle or shotgun butt.

firing-pin bushing

A hardened steel bushing let into the breech face of a firearm and containing the firing-pin hole. Usually also functions to limit firing-pin protrusion.

extractor

A hooklike part that catches the rim of a cartridge or fired case and pulls it partially or completely out of the chamber. As a rule, the extractor doesn't eject the round or case from the gun. See ejector.

duplex loads

A loading term normally used when more than one type of powder (usually of different burning rates) is used in loading the same cartridge to obtain maximum performance. Generally, duplex loads should be avoided

CB cap

A low-powered .22 rim-fire cartridge that uses only the primer for power

bolster

A lug or recess on the breech of a muzzleloader into which the nipple is screwed.bolt The assembly that houses the striker and case extractor mechanism and locks the cartridge or shell in the firearm's chamber. In a shotgun, the sliding or rotating extension that engages bites in the lumps or barrel extensions to lock the action body.

extended magazine release

A magazine release with a lengthened or enlarged finger button.

ambidextrous safety

A manual safety with a lever/thumbpiece on each side of the frame or receiver so that the shooter can operate it with either hand.

extended safety

A manual safety with the thumbpiece extended forward and/or outward more than normal.

extended slide stop

A manual slide stop with an extended thumbpiece. This is an accessory of questionable value and should never be used on a serious weapon.

extrusion

A material-forming process whereby the material is forced through a die for desired shape.

automatic safety

A mechanical device on any firearm that's engaged automatically either by cocking or by loading the gun. Prevents firing until the safety is manually disengaged.

firing-pin block

A mechanical stop or interlock that prevents a firing pin from reaching the primers until it's disengaged by linkage with the sear, hammer, or trigger at the instant of firing.

double-set trigger

A mechanism containing two triggers. One operates as a cocking trigger requiring heavy trigger pull pressure, while the other trigger functions as a firing trigger with an adjustable and very light pull.

barrel band

A metal band used on rifles that holds the stock and barrel, or barrel and magazine tube, together.

escutcheon

A metal or plastic insert in grips to provide a more secure seat for screws. Sometimes applied to trademark emblems inletted in grips.

antimony

A metallic chemical element used for hardening lead alloy and other metals. Most lead bullet cores use up to 3% antimony.

clock system

A method by which a clock face is used to designate the bullet strike on a target or to indicate wind direction. The center of the target would normally represent the center of a clock, with the top center position indicating 12 o'clock, bottom center 6 o'clock, center right 3 o'clock, and center left 9 o'clock.

etching

A method of embellishing metal gun parts. First, they're coated with a special varnish. Then the gunsmith or artist scribes through the finish. Next, the part(s) are put in an acid bath. The acid eats away some of the exposed metal, and when the varnish is stripped away a decorative pattern is left.

bore sighting

A method of preliminary sighting-in of a rifle, usually of bolt-action design. The bolt is removed and the rifle is mounted firmly with the target centered when viewed through the bore. The sights are then adjusted until they, too, bear on target.

draw-file

A method used to smooth gun barrels in which a long file is drawn at right angles to the length of the barrel. Commonly used in refinishing military rifles.

fanning

A method whereby a single-action revolver is fired rapidly. The trigger is held back, allowing the hammer to rapidly and repeatedly drop and fire the gun as the palm of the other hand strokes (fans) the hammer to the cocked position. It's not possible to fan double-action revolvers. As a rule, fanning should be discouraged because it can damage the gun

assault rifle

A military weapon that has the following characteristics: (1) short overall length (may have folding stock); (2) uses a short cartridge of intermediate power; (3) has both full and semiautomatic modes; and (4) is able to use large capacity box magazines or drums. See military pattern rifle.

bolt (cylinder stop)

A movable stud protruding through a revolver frame into a notch in the cylinder, which holds the cylinder in alignment with the barrel.

combustible cartridge

A muzzle-loading cartridge containing powder and projectile rolled in a nitrated paper casing, making the entire cartridge completely combustible.

flintlock

A muzzle-loading gun fired by means of a piece of flint, held in the hammer or cock jaws, striking against a steel frizzen. Incandescent particles of steel scraped from the frizzen fall into a pan holding powder. This ignited powder flames through the touch-hole, thus firing the main charge.

extended ejector

A n ejector with a lengthened finger on the front. May reduce jams by expelling the fired case sooner during the slide's cycle. Usually used on Colt government model style pistols.

cordite

A nitroglycerine, double-based, smokeless powder of nitroglycerine and gun cotton used in the form of long, thin spaghettilike strands or cords; used mainly in Great Britain.

ballistic coefficient

A number given a bullet that "rates" the ability of that bullet's design to overcome air resistance in flight.

case

A paper, metal, or plastic container that holds all other components of a round of shotgun or rifle ammunition: powder, primer, wad, and projectile. Normally referred to as a shell in shotguns, and when empty, a hull (slang).

cylinder latch

A part, usually actuated by one's thumb, to disengage the cylinder of a revolver so the arm may be opened for loading and unloading and extraction of fired cases.

chamber indicator

A pin, button, or lever that's forced outward when a cartridge is chambered in a firearm to indicate the gun is fully loaded. May be a separate part or a design function of the extractor

burr hammer

A pistol hammer with a short, rounded thumb spur-sometimes with a hole drilled through it. Also called commander hammer and combat hammer

C press

A popular cartridge reloading press, so named because of its shape.

Director of Civilian Marksmanship (DCM)

A position established under the National Defense Act within the National Board for the Promotion of Rifle Practice, to promote civilian rifle marksmanship. Established in 1916.

A hooklike part that catches the rim of a cartridge or fired case and pulls it partially or completely out of the chamber. As a rule, the extractor doesn't eject the round or case from the gun. See ejector.

A primer whose primer cup metal has been forced back into the firing pin hole in the face of the bolt, or a primer that extends entirely above the cartridge base. Usually denotes excessive pressure, soft primer metal, and/or excess headspace.

boxer primer

A priming system in which the primer contains its own anvil pressed into the cup. The standard type of primer used in all shotshells and centerfire cartridges manufactured in the United States. Named after the inventor, Col. Edward Boxer.

deplating

A process for removing chrome, nickel, silver, tin, or other plated finishes by a mechanical, chemical, or electrical process.

barrel tang (hood)

A projection at the upper rear of an auto pistol barrel that controls relative longitudinal positions of barrel and slide when in battery. Also aids feeding.

boss

A protrusion on a part, to house other parts or to maintain alignment with related parts.

barrel lug

A protrusion on the barrel for attachment of accessories or to house other parts.

double-base powder

A quick-burning, smokeless, propellant powder with nitroglycerin and nitrocellulose. Cordite is an example of a double-base powder

cheekpiece

A raised portion on the buttstock of any long gun, intended to ensure a good cheek-to-stock contact during shooting.

copper

A reddish-brown, malleable basic metallic element in such alloys as bronze, brass, or gilding metal.

burning rate

A relative term denoting the rapidity with which a given powder burns compared to other powders.

crimp remover

A reloading device to remove the crimp in the primer pocket of a military case by swaging. Crimps may also be removed by reaming.

crimp die

A reloading die that crimps the case mouth to the bullet or folds the front of a shotgun shell.

false muzzle

A removable extension of the barrel usually associated with high-grade target guns of the late muzzleloading and early breech-loading period. False muzzles are generally used in cases where maximum accuracy is desired, as they serve to protect the rifling at the muzzle during the use of the ramrod when seating the bullet. They must be removed before firing.

express rifle

A rifle that uses and fires express cartridges. Most were made between the late 1870s through the early 1900s.

carbine

A rifle with a short barrel. Also used to describe a light, short, limited range M-1 (semiautomatic) or M-2 (automatic) rifle once used by the U.S. Armed Forces. Older carbines may have barrels up to 30 inches. Currently, the word refers to lengths from 16 inches (the legal minimum) to 20 inches.

bench rest rifle

A rifle, usually with a heavy barrel, that's designed for maximum accuracy. These rifles are usually shot from a fixed benchrest, thus eliminating much human error.

flanged

A rimmed cartridge case

ejector rod

A rod or plunger designed to eject fired cases out of the chamber. Usually used on solid-frame revolvers.

ball

A round lead projectile, still commonly used in blackpowder muzzle-loading arms and cap & ball revolvers. The term is also used within the military services to describe ordinary cartridges. However, modern ball ammunition is loaded with a bullet, not a ball.

clay bird

A saucer-shaped disk made from a claylike material used in most shotgun shooting games. Also known as clay pigeons and clay targets.

ball screw

A screw device which, when attached to the end of a ramrod, can be threaded into a ball in the breech end of a muzzleloader. The ball can then be removed by withdrawing the rod.

chamber reamer

A sharp-edged tool used to cut or enlarge a cartridge chamber(s) in a barrel or cylinder.

barrel adapter

A short section of chambered barrel which, when inserted into a larger caliber barrel, permits the firing of a smaller caliber cartridge. Also known as a subcaliber device.

barrel bushing

A short sleeve in the muzzle end of an auto pistol's slide intended to support the barrel. It may be fixed (Browning) or removable (Colt).

blown pattern

A shotgun pattern with erratic shot distribution, generally caused by gas bypassing the wad and disrupting the shot cone.

crazy quail

A shotgun sport in which the shooter is positioned within a partially enclosed booth that limits his or her field of fire to the rear while standard clay targets are thrown from an underground trap in any direction

English stock

A shotgun stock common to British field guns that's distinguished by a straight grip versus the pistol grip found on other (especially American) shotgun stocks.

compression-formed shotshell

A shotshell design whereby the entire plastic case is formed in a single piece from a mold. This design eliminates the separate head, body tube, and base wad of earlier designs.

burp gun

A slang term for submachine guns.

combat underlug

A sleeve that slips over a revolver barrel and is fastened to it. Adds extra weight, and may or may not include an optional muzzle compensator. Used on target guns.

chamfer

A slightly beveled edge or rounded angle placed on a cartridge case mouth to facilitate bullet seating and to remove outside burrs from the case. Can also refer to the beveling of any edge, angle, or hole.

deloader (unloader)

A small device primarily used to unload a muzzleloader. They usually work by expelling the unwanted ball (and powder charge, if there is one) with compressed air or CO2 gas. There have been limited applications with breech-loading cartridge arms. Be careful! Whatever is in the bore may be ejected with enough force to cause injury.

belly gun

A small, compact revolver or pistol intended to be carried concealed.

call, game

A sound produced orally or by a mechanical device to attract wild animals, birds, waterfowl, or predators.

canister

A standardized container used by powder manufacturers.

crooked stock

A stock used by visually impaired shooters. It's an offset stock, usually bent or shaped into an S curve so that the arm may be fired off the right shoulder with the barrel aligned with the left eye or vice versa. See cross-eyed stock.

flint

A stone located in the cock of the flintlock that strikes steel, causing a spark to ignite the powder.

case hardening

A surface-hardening process, sometimes involving the use of dangerous cyanide compounds. The procedure leaves a very hard, thin, wear-resistant surface on iron-based alloys that may (or may not) show mottled "old-time" colors rich in yellow, brown, blue, and gray.

center of impact

A term applied to the calculation and measurement of a horizontal and vertical displacement and subsequent location of the precise center of a given group of shots on a target.

copper-jacketed

A term commonly applied to bullets made with pure copper jackets or to bullets with copper-colored gilding metal jackets.

DEWAT

A term generally applied to machine guns, submachine guns, or other fully automatic weapons rendered unserviceable by welding or cutting. An acronym for DEactivated WAr Trophy.

accuracy

A term used to describe the ability of either a firearm or ammunition, or a combination thereof, to shoot consistently where aimed.

barrel liner

A thin-walled, rifled tube used for relining worn barrels or changing to another caliber.

breech plug

A threaded plug that closes the breech end of the bore in a muzzleloader's barrel.

drilling

A three-barreled combination gun, usually of German or Austrian manufacture. Generally, it has one rifle barrel mounted under two side-by-side shotgun barrels.

barrel bushing wrench

A tool designed to fit over a pistol's barrel bushing and provide extra leverage to turn it for removal or replacement. Used when the bushing is especially tight inside the slide.

Cosmoline

A trade name used to identify a protective, rustpreventive grease used on ferrous metal parts; formerly used by the military services.

double pull

A trigger action commonly found in military rifles whereby the gun trigger is moved some distance with little finger pressure. Then, considerably greater trigger pull pressure is required for a relatively short distance to release the sear.

combat guard

A trigger guard reshaped at the front to provide a secure seat for the off-hand forefinger in two-hand pistol shooting.

choke tube

A tube screwed into the muzzle or choke body that provides a particular degree of choke.

cake cutter

A tubelike device, most often a fired cartridge case with its head cut away, used to remove cast lead bullets from a block of molded lubricant. Also spelled kake kutter

blowback action

A type of action design in which the bolt or slide isn't locked. Rather, the breech is held closed by the weight and inertia of the bolt combined with recoil spring tension. The majority of semiautomatic pistols chambered for cartridges between .22 through .380, .22 semiautomatic rifles, and most submachine guns use some form of blowback system.

centerfire (abbreviated CF)

A type of ammunition that has a centrally located primer or system of ignition in the base of a cartridge case and is generally reloadable. This is distinguished from priming compound located in the rim of the cartridge case (known as rim fire).

boat tail

A type of bullet, usually long and slender with a high ballistic coefficient, which is tapered at the base. Used frequently for long-range shooting and as military and match bullets.

box lock

A type of gun lock originating in muzzle-loading guns and still used in many modern break-open shotguns. All the working parts are contained within the action body itself. The hammer(s) may be either internal or external.

air gun

A type of gun that uses compressed air or gas to launch a pellet, dart, or shot charge.

Berdan primer

A type of ignition system in which the anvil is part of the cartridge case rather than the primer. These cases can be easily identified because they have two flash holes inside the primer pocket. The system was invented by an American, Col. Hiram Berdan, in the 1860s.

buckhorn sight

A type of rear sight in which the sides of the leaf curl upward and inward over the sighting notch, similar in shape to a bull's horns.

bolt action

A type of rifle action consisting of a tubular receiver fitted with a cylindrical, manually operated bolt which incorporates either front or rear locking lugs.

BB

A type of round. A .177 diameter air rifle projectile usually made of iron. Also a shot size sometimes used for hunting geese.

back action side lock

A type of shotgun side lock action in which the entire mechanism is behind the action body.

combat sight

A very general term referring to fixed or adjustable target-type sights featuring low-profile, minimum bulk, and often have colored or luminescent inserts (dots, bars, etc.) to enhance quick visual "pick-up" under any light condition.

flash

A very minor explosion on a flintlock resulting when a bit of molten metal falls into the priming powder in the flash pan

collimator

A very precise device used for checking the precision and accuracy of optical devices such as scope sights. In shooting, an optical instrument attached to the muzzle, used to align telescopic sights on rifles or pistols.

CF

Abbreviation for centerfire. Usually refers to a centerfire cartridge.

Deringer, Henry

An American gunsmith (1786-1868) who produced a famous short single-shot percussion pistol, starting in 1825.

brass

An alloy of copper used to manufacture cartridge cases and bullet jackets; also a term commonly applied to empty cartridge cases.

Damascus barrel

An early form of barrel construction formed by welding together strips of various metals around a mandrel. Damascus barrels were once considered the ultimate in fine craftsmanship. However, even with the best possible construction, they're considered inferior to fluid steel barrels, at least those made after the early 1900s.

blunderbuss

An early muzzle-loading gun with a flared muzzle. Traditionally pictured as the standard Pilgrim firearm, which is absolutely erroneous. Actually, the blunderbuss was more commonly used on naval vessels to discourage boarding of unwanted passengers or pirates, and to protect stagecoaches against highwaymen. They were the original "sawed-off shotguns."

CO-AX press

An in-line type of reloading press developed by the Bonanza Tool Company, now manufactured by Forster Products, Inc.

chronograph

An instrument used to measure the velocity of a projectile.

double rifle

Another term for double-barreled rifle.

bullet, expanding

Any bullet designed to deform or expand in a predictable manner upon impact.

charger

Any device (flask, horn, dipper, etc.) that measures out one exact charge of powder.

breechloader

Any firearm in which loading is accomplished from the breech. Breech-loading firearms date back to the 1400s, although they were considered "new" in the 1850s when they superseded muzzleloaders.

double-barreled gun

Any gun having two barrels

decoy

Any likeness of a bird or other hunted species replica used to attract others of its species within shooting range. Decoys have been used successfully from earliest times to attract a variety of game and varmints. Live bird decoys, once widely used, are now illegal for the most part.

bull barrel

Any rifle or handgun barrel that's abnormally thick and heavy for its length. A heavy target barrel.

altitude effect

As altitude increases and air has less density, bullet drop decreases due to lessened air drag or friction.

BT

Boat tail, referring to the base taper given certain bullets to give them greater efficiency at long ranges

barrel cam

Cam surfaces in the barrel or frame that serve to lock and unlock the breech.

carving

Designs cut into the wood portion of a firearm

cook off

Encountered with machine guns and other fullautomatic weapons; the firing of a cartridge resulting from igniting the primer by an overheated chamber due to extensive rapid firing. Won't occur in a machine gun such as the Thompson, which fires from an open bolt.

creep

Excessive motion or movement between full-finger pressure and sear release during trigger pull. Also called drag or crawl.

cupronickel

Formerly used for bullet jackets, this material contains about 60% copper and 40% nickel.

dud

Generally referred to as a misfired cartridge; however, it can apply to any explosive charge that doesn't detonate as intended.

breech block

Generally used in single-shot small arms. The part of the breech mechanism that locks the action against pressure of the fired cartridge.

accurize

Improving the accuracy of a handgun or rifle by individually fitting or replacing certain parts. In semiautomatic pistols, this usually involves a better lock-up between the barrel and slide; in rifles, precise bedding between the barreled action and stock

big-bore

In American target shooting terminology, usually refers to .30 caliber rifles; with handguns, to a bullet diameter greater than .38 caliber; and with hunting rifles, to cartridges above .30 caliber.

barrel flats

In a double shotgun, the flat portions at the breech or rear end of the action body (water table).

cap groove

In a percussion revolver, clearance cuts in the recoil shield to allow easy application of caps and to provide clearance for fired caps.

brisance

In a propellent, such as blackpowder, that quality of brusqueness or shattering power. The more brisant an explosive, the more rapidly it detonates, and the greater its relative power of demolition.

double action

In a revolver or autoloading pistol, the action by which the hammer can be cocked and dropped to fire the gun by a single pull of the trigger.

cylinder

In a revolver, a cylindrical carrier that rotates (generally) around an axis parallel to and below the barrel of the revolver. Contains chambers for several cartridges (usually six) and combines the functions of a magazine and feed system.

end play

In a revolver, undesirable fore and aft motion of the cylinder

barrel extension

In a short-recoil autoloader, a tubular member attached to the rear of the barrel, containing the breechbolt. Not common, but found in Luger (Parabellum), Mauser M96, and Auto Mag pistols.

bar action side lock

In a shotgun, a system of side lock design in which part of the working parts of the gun are on a plate that extends up to and into the bar of the action body.

bar

In a shotgun, the forward extension of the action body, the top of which is the water table or flats.

field of view

In a telescopic sight, the maximum area or optimum view through the scope, usually measured at a distance of 100 yards

crosshairs

In a telescopic sight, the sighting lines

energy

In bullets, the amount of work done, at given ranges, expressed in foot pounds. The amount of work capable of being done (force transferred) by a projectile at a given range, expressed in foot pounds.

action

In general, the primary assembly of a firearm consisting of the receiver, bolt or breech block, and feed and firing mechanisms. The operating mechanism to which the barrel and stock are attached. In a double-barreled shotgun, the action refers to the receiver that houses the working parts, commonly called the action body.

bore diameter

In rifles and handguns, it's determined by measuring the distance from land to land (raised portions) of the bore. To put it another way, it's the measurement from one side to the other before rifling is cut.

bites

In shotguns, slots cut in either barrel extensions or lumps into which bolts fit to lock the gun together.

Colt, Samuel (1814-1862)

Invented what would become the first commercially successful revolver, and was issued patents in 1836. His original venture at Paterson, NJ, went bankrupt. However, Colt's repeating arms were popular in Texas, and demands from that quarter provided enough incentive to put him back in business by 1847. The Colt Patent Firearms Manufacturing Company was chartered at Hartford, CT, in 1855.

flush-seating

Loading a wadcutter bullet completely within the case, its nose flush with the case opening.

barrel lugs

Located on the underside of the barrel. Provides the means for attaching the forearm to the barrel.

bullet lubricant

Lubricating grease applied to a lead bullet to decrease friction, prevent leading, and reduce deformation

checkering

Made by cutting diamondlike patterns on grips and forends of rifles and shotguns and sides of handgun grips. Checkering is usually done by cutting crossing diagonal lines with either files or special machine cutters. Also done to metal parts, such as front and back straps of pistol frames, front faces on trigger guards, etc

ammunition

Made up of the following components, which together comprise a cartridge: case, primer, bullet (or shot), and powder charge.

bullet mold

Metallic device with a cavity(s) into which molten lead (or lead alloy) can be poured and allowed to harden into a projectile.

combat conversion

Modifying a rifle, handgun, or shotgun normally used in a sport-shooting context to make it a more effective weapon. Such arms may be used for combat purposes, or in certain games that more or less simulate combat situations.

combat trigger

On Colt government model pistols: A trigger with a long fingerpiece, usually made from lightweight material and further lightened by removing material (holes, slots, etc.). Most include a stop screw. They may be a useful option on game guns, but have little or nothing to do with combat.

ejectors

On a double- or single-barrel shotgun, a mechanism similar in design to a miniature gun lock, activated by the falling of one or both hammers within the action, which will selectively eject the emptied or fired shell clear of the gun. Ejectors are usually cocked by the closing motion of the gun.

box magazine

On a rifle, a boxlike feed device containing cartridges, one stacked on top of the other. Usually removable for reloading. Sometimes erroneously referred to as a "clip." See clip.

drop, stock

On shotguns or rifles, the measurement of the slope (drop) of the top of the buttstock from the line of sight. Drop is necessary to bring the sight to eye level.

cannelure

One or more grooves cut around the circumference of a bullet or cartridge case. In reference to bullets, cannelures are used to hold lubricant, furnish identification, help control expansion, and/or furnish a point on the bullet where the case neck can crimp. Cannelures may be used on cartridge cases to help secure the bullet and/or prevent it from being pushed backwards during the feeding cycle.

combat matches

Originally intended to simulate real-life situations and use practical equipment. Today's so-called combat matches seldom resemble that ideal. This is of no importance, except one should understand that the guns and other accessories that are used have little or no application as real weapons. See action shooting.

conversion unit

Parts to be assembled to an existing gun to change its caliber or configuration; e.g., Colt .22 conversion unit for .45 caliber government model.

ear protectors

Plugs, ear-fitting valves, acoustical muffs, or similar products that help protect the shooter's ears from injury resulting from gunfire noise.

beavertail forend

Refers to a forend that's wider than normal. Provides for a better grip and protects the hand from a hot barrel during rapid shooting.

bedding

Refers to the fit between a rifle's barrel or barreled action and the stock. The stock may be inletted to receive the metal parts, or a void may be carved out and filled with reinforced epoxy material called glass bedding.

fit and finish

Refers to the overall craftsmanship of a gun.

bore buildup

Refers to the powder or metal fouling residue resulting from continuous firing or lack of cleaning of a rifle, shotgun, or handgun

case capacity

Refers to the usable case volume; that part of the case interior below the base of the case neck.

buckshot

Round lead balls, running from No. 3 (.25 diameter) to No. 000 (.36), which are loaded into shotgun shells and used for hunting big game at close range, or in military and law enforcement applications.

cylinder stop

See bolt.

color-harden

See case hardening.

crane (yoke)

That part in modern double-action revolvers to which the cylinder is attached and which can be pivoted to the left for loading and unloading.

cartridge case

That part of a cartridge or shotgun shell that contains the primer, powder, wads, and bullet (or shot).

anvil

That part of a primer against which the priming mixture is crushed by the firing pin, thereby producing detonation.

chamber

That part of the bore (or cylinder, in a revolver) that's enlarged to accept a cartridge or shell.

bearing surface

That portion of a bullet's surface that contacts the barrel or rifling in its passage through the bore. Sufficient bearing surface is necessary for good accuracy.

breech face

That portion of a revolver frame or autoloader slide which supports the cartridge head upon firing.

feed ramp

That portion of the barrel and/or frame that guides the bullet's nose in a loaded cartridge from magazine to chamber.

barrel tenon

That portion of the barrel, usually threaded, which fits into the receiver.

air space

That space between the powder and bullet in a loaded cartridge. Most commercial cartridges contain 10% to 15% airspace because of loading machine mechanical requirements.

calling the shot

The ability of some shooters to know where each shot has struck without inspecting the target. Depends on knowing the exact sight alignment at the instant of firing.

feeding

The act of positioning, usually by the magazine, of the cartridge in line with the chamber in preparation for chambering.

combustion

The act or process of burning; the chemical process that unites oxygen with other substances in gunpowder to produce heat and gas.

eject

The action whereby a cartridge is thrown clear from the breech after extraction

charge

The amount of propellant or powder loaded or measured into the case. Also refers to the act of loading or charging.

caliber (calibre)

The approximate bore or groove diameter (land-to-land diameter) of any gun barrel, expressed in one-hundredths of an inch or in millimeters. This measurement is frequently compounded to indicate the powder charge in the case of old black 45 powder cartridges, such as 38-40, 45-70, etc. The first number is the caliber, the second, its charge of powder measured n grains.

engraving

The art of hand-cutting patterns or designs into the metal parts of a firearm, greatly enhancing its value.

crimp

The bending inward of the case mouth perimeter, in order to grip and hold the bullet, or to keep the shot in a shotgun shell intact.

drift

The bullet's movement to right or left, away from the line of the bore, caused by bullet rotation or spin.

core

The central portion of a bullet, usually lead, that's covered by a jacket.

deterrent

The combustion-controlling chemical materials added to an explosive or gunpowder to reduce its burning rate and produce desired burning characteristics.

case, separated

The condition of the case head cracking away from the case body. Also called a ruptured case.

choke

The construction at the muzzle of a shotgun barrel designed to control the spread and dispersal of the shot charge.

ball powder

The copyrighted trade name for a double-based, smokeless propellant developed by Olin Industries for the U.S. military. Ball powder may be either flat or spherical in shape.

ejector

The device(s) at the barrel breech or within the action that knocks the fired case from the gun. See extractor.

bullet deflection

The directional deviation produced when a bullet strikes any object and is deflected from its original path. Also referred to as ricochet.

drop

The distance a projectile falls (measured or calculated from its line of departure) due to the force of gravity. This must be corrected for differences between the line of sight and the line of departure.

barrel travel

The distance traveled by the barrel in locking and unlocking in a recoil-operated auto pistol.

blackpowder

The earliest small arms ammunition propellant. Made from saltpeter (potassium nitrate), charcoal, and sulphur. The original mix is thought to be a Chinese invention. Today, blackpowder is used in reproduction muzzle-loading firearms.

corrosion

The eating away of metal in a rifle or shotgun bore by rust, caused by salts deposited by primer or powder. Also, rust on any metal surface caused by exposure to salt air or moisture.

chamber pressure

The expanding gases that force the bullet or projectile out of the case, into the barrel, and down the bore. Chamber pressure is created when the powder propellant is ignited.

bolt thrust

The force exerted on the face of the bolt by the pressure of powder gases.

bolt face

The forward end of the bolt, containing the firing pin and extractor, that supports the base of the cartridge when chambered.

air resistance

The friction or drag that slows the forward motion of a projectile and limits its maximum range. A bullet's relative ability to overcome this resistance is defined by its ballistic coefficient number.

cylinder gap

The gap located between the cylinder and barrel breech in a revolver

erosion

The gradual wearing away of metal from surfaces within a gun barrel by the heat of powder gases and bullet friction. This condition starts just ahead of the chamber and proceeds down the bore. It's sometimes mistaken for corrosion (which it isn't, although you may see a combination of the two). Eventually, erosion will adversely effect both accuracy and velocity. The only cure is to set the barrel back and rechamber it, or replace it entirely.

barrel channel

The groove cut in the forward portion of the stock to accommodate the barrel.

bullet engraving

The grooves impressed in a bullet by the rifling lands as the bullet is driven through the barrel.

aperture

The hole, or its diameter, in a peepsight eyepiece. Or, the word may apply to the eyepiece itself. Also, some front sights intended for bull's-eye target shooting are fitted with an aperture disk or insert that has a round opening that can be centered on the bull's-eye image.

click

The increment of adjustment in adjustable sights. Provided by a spring or ball detent engaging notches in the adjustment screw. Of no established value, but each click normally produce less than a 1 inch change at 50 yards, dependent upon manufacturer.

bore

The inside of a firearm barrel

flinch

The involuntary movement or jerking of a firearm by shooters as they fire or anticipate firing a gun. The condition is often caused by conscious or subconscious fear of noise or recoil.

bullet energy

The kinetic energy, generally stated in foot/pounds, delivered by a bullet at impact.

back thrust

The load exerted rearward on the breech face when a cartridge is fired. May be calculated by multiplying chamber pressure by case head area.

firing-pin protrusion

The measurement from the bolt face to the tip of the firing pin as it protrudes beyond the face of the bolt at the instant of firing.

floor plate

The metal plate located at the bottom of the cartridge magazine. May be fixed, hinged, or detachable, depending on gun type. Sometimes called the bottom or base piece.

bullet pull

The number of pounds required to extract a bullet from a loaded cartridge, thus measuring how tightly the case neck grips the bullet.

Amateur Trapshooting Association (ATA)

The official regulating and rule-setting organization for registered trapshooting, with headquarters in Vandalia, Ohio.

flashhole

The opening between the pan of a flintlock and the powder charge in the chamber.

exit pupil

The opening or clear aperture in the eyepiece lens of a telescopic sight.

eye relief

The optimum distance a shooter must hold his or her eye from the ocular lens of a telescope to obtain a full field view through the scope.

engine turning

The overlapping pattern of circular spots appearing on the bolts of rifles and shotguns, formed on the bolt surface by a spinning abrasive rod. Often incorrectly termed damascening

breech bolt

The part of a breech that resists the rearward force of the combustion that occurs when a cartridge is fired.

expander

The part of a die that expands the case mouth to receive the bullet. Also referred to as the expander ball.

barrel

The part(s) of a gun through which bullets or shot pass, traveling from breech to muzzle through the bore.

components

The parts that make up the cartridge, such as bullet, cartridge case, powder, primer, and so forth.

fine sight (fine bead)

The picture in an open sight when the tip of the front sight shows only slightly at the base of the notch of the rear sight.

decapping pin

The pinlike rod in an expander die or sizer that expels the spent primer from a fired case.

breech

The portion of a gun which includes the essential working parts: the action, trigger or firing mechanism, magazine, and chambered portion of the barrel. In modern arms, that portion of the barrel through which the cartridge is inserted.

case forming

The process of making cases of one size suitable for another. Usually accomplished mechanically by special loading press dies. See fire forming.

extract

The process of removing the fired case from the chamber as the action is opened.

cock

The process of setting the action or firing mechanism into firing position. Some weapons have a half-cock position that sets the action in an intermediate position. On early weapons the hammer was referred to as a cock.

annealing

The process of softening metal by heating. Makes brass cartridge cases more malleable, less brittle, and prevents cracking from repeated resizing. Spot annealing of a receiver is sometimes necessary to permit drilling and tapping for scope mount installation.

crown

The radiused, recessed portion of a barrel muzzle which protects the edge of the bore from impact damage.

cyclic rate

The rate at which a full-automatic weapon will fire ammunition. Usually expressed in rounds of ammunition per minute.

expansion ratio

The ratio of the volume of the bore (from the base of the seated bullet to the muzzle) to the volume of the cartridge case. An expansion ratio of 10:1 means the bore volume is 10 times the cartridge case volume.

back strap

The rear portion of that part of a handgun frame to which the stocks are attached.

cone

The rear portion of the choke at the shotgun muzzle. Also, the front tapered portion of a shotgun chamber in which the diameter is decreased to bore diameter.

buttstock

The rear segment of a two-piece rifle or shotgun stock, or that portion of a one-piece stock that extends backwards from the action

bolt guide

The rib or groove that maintains alignment during bolt travel, with the corresponding part located either on the bolt or on the receiver.

ballistics

The science dealing with the motion, behavior, and impact of projectiles. Interior ballistics concerns itself with what occurs inside a gun from primer ignition to departure of the projectile from the bore. Exterior ballistics is concerned with the bullet's flight. Terminal ballistics relates to a bullet's performance when it strikes or enters a target.

fire-form

The shaping of a cartridge case to fit a given chamber by firing the case in that chamber.

barrel link

The short pivoting piece that's cross-pinned to a lug on the bottom, rear part of the barrel. The link pulls the barrel down, causing it to unlock from the slide during the reloading cycle. It's used in Colt's government model, including variations, copies, and clones.

brazing

The soldering of metal parts by use of a copper alloy (usually brass). Often used to mount sights and lugs to shotgun barrels, and for many gun repairs.

barrel/cylinder gap

The space between barrel and cylinder of a revolver, essential to smooth operation. Normally about .006 inch.

battery cup primer

The standard-type primer used in most shotgun shells.

Cap-Shur gun

The trade name for a gun specifically designed to launch hypodermic-type darts containing tranquilizer drugs. Generally used to subdue wild animals

feed lips

The upper edges of a magazine that position and guide the cartridge during feeding and chambering from the magazine.

comb

The upper portion of a buttstock on a rifle or shotgun that serves as a rest for the shooter's cheek as well as an alignment point for the shooter's eye.

blueing

The various blue-black finishes applied to ferrous metals for appearance and rust prevention. The blueing process oxidizes a thin surface layer of the metal. There are a variety of blueing methods, but the quality and texture of finish depends on the degree and type of polishing.

elevation

The vertical sight adjustment to bring the point of aim to the proper elevation to compensate for bullet drop.

barrel erosion

The wearing or washing away of metal just forward of the chamber by hot powder gases. The degree depends on how much chamber pressure is generated, the amount of powder burned per shot, and the level of heat that develops. Erosion reduces accuracy, and in an extreme case may cause a bullet to disintegrate.

dehorn

To cut off the hammer spur and other nonessential projections from a handgun (especially revolvers), which may be carried concealed to prevent catching or snagging on clothes.

decap

To deprime or remove the primer from a fired cartridge case.

deburr

To remove rough edges or small metal burrs, specifically from the inside and outside of a cartridge case mouth.

deprime

To remove the fired primer from a cartridge case.

Double-Ace

Trade name for an unusual device that allows cocking the Colt government model pistol by squeezing a lever at the rear of the grip. Manufactured by Caraville Arms.

action shooting (action matches)

Two terms used by those who, for whatever reason, dislike the word combat. Generally, the shooting sports designated action or combat require the competitor to start with their handgun holstered, to draw and fire, and to hit one or several targets while they move about. The winner makes the required hits in the shortest time.

die

Used in hand-loading forming tools, to form or reform cases and bullets and for extruding lead wire, drawing jackets, or swaging bullets or cores in the manufacture of ammunition. In reloading, a tool for resizing cases or seating bullets.

dummy cartridge

Used to test-feed ejection mechanisms in firearms. A dummy cartridge usually consists of a cartridge case, bullet, and uncharged primer, forming an inert round.

bullet trap

Usually a steel box especially made to receive, decelerate, and stop bullets without ricocheting or deflecting fragments. A sandbox, cotton padding, or water receptacle may be used.

cocking lever

Usually an internal lever that acts to force the hammer or hammers to the cocked position as the action is opened. Occasionally, the cocking lever will be found on the outside of a receiver and is operated manually to cock or uncock an internal firing mechanism.

crimped primer

Usually found in military cartridges, it's a primer that's been secured in the primer pocket by a flange indented from the mouth of the pocket

fast draw

Usually refers to a game in which the contestant draws a specially modified single-action revolver from an equally specialized belt and holster. Ammunition is limited to blank cartridges or ones loaded with nothing more than a primer and wax bullet. The idea is to stop a timer or hit a target in the shortest possible time. Championship records have run as short as 0.2 seconds. The term may also be used to describe the process of quickly drawing a handgun from a holster and firing. Any such practice should be conducted with extreme care.

breath control

Vital to accuracy, as the barrel and sights move with each breath the shooter takes. After the position is steady and the sight picture good, the shooter takes a full breath, lets half out, holds, and squeezes the trigger

beavertail grip safety

beavertail grip safety

Ferguson rifle

e The first practical breech-loaded rifle designed and patented by Major Patrick Ferguson (1744-1780). The gun is simple in design, consisting of a round breech plug passing through a matching hole at the rear of the barrel, and caused to travel vertically by means of a multiple high-pitch thread. Few Ferguson rifles are in existence today.

drams

equivalent A term used in shotgun ballistics to indicate that a charge of smokeless powder produces the same velocity as a stated volumetric charge of blackpowder.

firing pin

part of the action, actuated by a spring or separate hammer, which strikes the primer and fires the cartridge.