Glossary

Click on a letter below to view the Glossary terms and explanations.

A


ACTION: The combined parts of a firearm that determine how a firearm is loaded, discharged and unloaded. Most handguns are referred to as "single-action" or "double-action." A single-action firearm requires the user to manually pull back the hammer before the firearm allows the user to either manually cock the hammer or simply pull the trigger and allow the firearm to cock and release the hammer on its own. The working mechanism of a firearm. Various types exist, including single-shots, multi-barrels, revolvers, slide- or pump-actions, lever-actions, bolt-actions, semi-automatics and automatics.


ACTION, AUTOMATIC: A firearm that loads, fires, and ejects cartridges as long as the trigger is depressed and there are cartridges available in the feeding system (i.e. magazine or other such mechanism). Automatic action firearms are machine guns. Note: Since 1934 it has been unlawful to sell or possess an automatic firearm without special permission and licensing from the U.S. Department of the Treasury, in addition to other measures.


ACTION, BOLT: A firearm, typically a rifle, that is manually loaded, cocked, and unloaded by pulling a bolt mechanism up and back to eject a spent cartridge and load another. Bolt action firearms are popular for hunting, target shooting, and biathlon events. A bolt action rifle allows the shooter maximum accuracy, but may be too slow or cumbersome for some shooting sports.


ACTION, LEVER: A firearm, typically a rifle, that is loaded, cocked, and unloaded by an external lever usually located below the receiver. Note: The type of rifle used in most Western movies is a lever-action.


ACTION, PUMP: A firearm that features a movable forearm that is manually actuated to chamber a round, eject the casing, and put another round in position to fire.


ACTION, SEMI-AUTOMATIC: A firearm in which each pull of the trigger results in a complete firing cycle, from discharge through reloading. It is necessary that the trigger be released and pulled for each cycle. These firearms are also called "autoloaders" or "self-loaders." The discharge and chambering of a round is either blowback operated, recoil operated, or gas operated. Note: An automatic action firearm loads, discharges, and reloads as long as ammunition is available and the trigger is depressed. A semi-automatic firearm only discharges one cartridge with each squeeze of the trigger.


 AMMUNITION: A loaded cartridge consisting of a primed case, propellant, and a projectile. Among the many types of ammunition are centerfire rifle and pistol, rimfire, shotshells, and reloads. This generally refers to the assembled components of complete cartridges or rounds i.e., a case or shell holding a primer, a charge of propellant (gunpowder) and a projectile (bullets in the case of handguns and rifles, multiple pellets or single slugs in shotguns). Sometimes called "fixed ammunition" to differentiate from components inserted separately in muzzleloaders.


 AMMUNITION, SMALL ARMS: A military term used to describe ammunition for firearms with bores (the interior of the barrel) not larger than one inch in diameter.


 ARMOR PIERCING: See BULLET, ARMOR PIERCING


 ARMS, SMALL: Any firearm capable of being carried by a person and fired without additional mechanical support.


 AIRGUN: Not a firearm but a gun that uses compressed air or CO2 to propel a projectile. Examples: BB gun, pellet gun, CO2 gun.


ANTIQUE: By federal definition, a firearm manufactured prior to 1899 or a firearm for which ammunition is not generally available or a firearm incapable of firing fixed ammunition.

 

ARMOR-PIERCING AMMUNITION?: By federal definition, "a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium. Such term does not include shotgun shot required by... game regulations for hunting purposes, a frangible projectile designed for target shooting, a projectile which the Secretary finds is primarily intended to be used for sporting purposes, or any other projectile or projectile core which the Secretary finds is intended to be used for industrial purposes, including a charge used in an oil and gas well perforating device."


 ASSAULT RIFLE: By U.S. Army definition, a selective-fire rifle chambered for a cartridge of intermediate power. If applied to any semi-automatic firearm regardless of its cosmetic similarity to a true assault rifle, the term is incorrect.


ASSAULT WEAPON: Any weapon used in an assault (see WEAPON).?? A political/legal term variously defined in laws, ordinances, and speeches. It usually includes semiautomatic arms superficially resembling assault rifles, but is also often defined to include pistols and shotguns.


AUTOMATIC: A firearm designed to feed cartridges, fire them, eject their empty cases and repeat this cycle as long as the trigger is depressed and cartridges remain in the feed system. Examples: machine guns, submachine guns, selective-fire rifles, including true assault rifles.


 AUTOMATIC PISTOL: A term used often to describe what is actually a semi-automatic pistol. It is, technically, a misnomer but a near-century of use has legitimized it, and its use confuses only the novice.

B


BALL: Originally a spherical projectile, now generally a fully jacketed bullet of cylindrical profile with round or pointed nose. Most commonly used in military terminology. 1. Spherical projectile 2. Ammunition with solid metal bullet, as opposed to blank, tracer, etc.


BALLISTICS: The science of studying projectiles. Ballistics can be "interior" (inside the gun), "exterior" (in the air), or "terminal" (at the point of impact). Ballistic comparison is the attempt to microscopically match a bullet or fired cartridge case to a particular firearm.


BARREL: That part of a firearm through which a projectile travels. The barrel may be rifled (i.e., with spiral grooves on the interior of the barrel) or smooth bore (i.e., a smooth interior barrel with no grooves).


BB: Spherical shot having a diameter of .180" used in shotshell loads. The term is also used to designate steel or lead air rifle shot of .175" diameter.


BEDDING: Fitting the metal parts of rifle to a wood or plastic stock. Often uses a glass fiber - epoxy resin combination ('glass bedding').


BENCHREST: A table specifically designed to eliminate as much human error as possible by supporting a rifle for competitive shooting or sighting-in purposes. A heavy table from which a rifle or pistol can be fired. 2. A heavy rifle made to be fired only from a bench rest. 3. Target competition won by the shooter who puts several bullets into the (single) smallest hole.


BIG BORE: In America, any firearm using a centerfire cartridge with a bullet .30" in diameter or larger.


BIRDSHOT: Small lead or steel pellets used in shotshells ranging in size from #12 (less than the diameter of a pencil point) to #4 (about .10" in diameter) used for short-range bird and small game hunting.


BLACKPOWDER: The earliest type of firearms propellant that has generally been replaced by smokeless powder except for use in muzzleloaders and older breechloading guns that demand its lower pressure levels.


BLANK CARTRIDGE: A round loaded with blackpowder or a special smokeless powder but lacking a projectile. Used mainly in starting races, theatrical productions, troop exercises and in training dogs.??
BLUING: Producing a thin layer of iron oxide on iron or steel to protect against rust. Usually done by immersion in hot salt solutions, but there are 'cold bluing' methods. A metal part to be blued later is "in the white."


BOLT-ACTION?: A gun mechanism activated by manual operation of the breechblock that resembles a common door bolt.


BORE: The interior of a firearm's barrel excluding the chamber.? The interior barrel forward of the chamber.


BORE DIAMETER: On rifled barrels, the interior diameter of the barrel from the tops of the lands (the highest point of the grooves). On a smooth barrel, the interior dimension of the barrel forward of the chamber (not including the chose on the shotgun barrels).


BRASS: A synonym for expended metallic cartridge cases: ??1. A zinc-copper alloy ('cartridge brass') 2. Slang for a cartridge case.


BUCKSHOT: Large lead pellets ranging in size from .20" to .36" diameter normally loaded in shotshells used for deer hunting.


BULLET: A non spherical projectile for use in a rifled barrel. The projectile expelled from a gun. It is not synonymous with cartridge. Bullets can be of many materials, shapes, weights and constructions such as solid lead, lead with a jacket of harder metal, round-nosed, flat-nosed, hollow-pointed, etc.


BULLET, ARMOR PIERCING: A projectile or projectile core that may be used in a handgun intended to pierce steel armor that is constructed entirely, or has a core constructed, from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, depleted uranium, or a fully jacketed projectile larger than 22 caliber intended for use in a handgun whose jacket has a weight of more than 25 percent of the total weight of the projectile. The term does not include shotgun shot or projectiles intended for sporting purposes. Note: The Gun Control Act of 1968 (18 U.S.C. Sec. 922 (a) (7)) prohibits the manufacture of sale of armor piercing ammunition, except for use by law enforcement and the military.


BULLET, DUMDUM: A British military bullet developed in India's Dum-Dum Arsenal in 1897-98. It was a jacketed .303 caliber rifle bullet with the jacket most left open to expose the lead core in hopes of greater effectiveness. Further development of the bullet was not pursued because the Hague Convention of 1899 outlawed and such bullets for warfare.


BULLET ENGRAVING: The grooves cut into a bullet by barrel rifling. Note: When a bullet travels down the barrel, the grooves (or rifling) leave an imprint on the bullet. The matching of the marks on a bullet to the rifling of a particular firearm is an important tool for law enforcement in determining whether a bullet was fired from a particular firearm.


BULLET, FULL METAL JACKET: A projectile in which the bullet jacket (a metallic cover over the core of a bullet) encloses most of the core with the exception of the base. They are used mostly for target shooting and military use.


BULLET, HOLLOW POINT: A bullet with a cavity in the nose, exposing the lead core, to facilitate expansion upon impact. Hollow point cartridges are used for hunting, self-defense, police use, and other situations to avoid over penetration.


BULLET, WADCUTTER: A generally cylindrical bullet design having a sharp shouldered nose intended to cut paper targets cleanly to facilitate easy and accurate shooting.


BUTT: On handguns, it is the bottom part of the grip. On long guns, it is the rear or shoulder end of the stock.

C

CALIBER: The nominal diameter of a projectile of a rifled firearm or the diameter between lands in a rifled barrel. In this country, usually expressed in hundreds of an inch; in Great Britain in thousandths; in Europe and elsewhere in millimeters.
The diameter of the bore; but for artillery and naval guns, the length of the barrel in numbers of diameters. For instance, a 5 inch 38 caliber gun would have a barrel 190 inches long. A term used to designate the specific cartridges for which a firearm is chambered. It is the approximate diameter of the circle formed by the tops of the lands of a rifled barrel. It is the numerical term included in the cartridge name to indicate a rough approximation of the bullet diameter (i.e. .30 caliber-.308" diameter bullet).


CARBINE: A rifle with a relatively short barrel. Any rifle or carbine with a barrel less than 16" long must be registered with the Bureau of Alcohol, Tobacco and Firearms. Shotguns with barrels less than 18" long fall into the same category.

 Typically a variation of a military rifle with a shortened barrel, used especially by mounted troops. Some carbines, though, do not have a longer version. The US M1 carbine, for instance, was not a shortened M1 rifle.


CARTRIDGE: A single, complete round of ammunition.


CASE, CASING: The envelope (container) of a cartridge. For rifles and handguns it is usually of brass or other metal; for shotguns it is usually of paper or plastic with a metal head and is more often called a "shell."


CENTER-FIRE: A cartridge with its primer located in the center of the base of the case.


CHAMBER: It was originally the part of the barrel that held the gunpowder. Now it is the part that holds the cartridge at the time of firing. The chamber is at the breech end of the barrel and may be enlarged somewhat to hold the cartridge. Revolvers have several separate chambers in a 'cylinder.'


CHOKE: A constriction at or near the muzzle of a shotgun barrel that affects shot dispersion. 
An interior tube at the end of a shotgun barrel that controls shot dispersion. Chokes typically come in cylinder, improved cylinder, modified, improve modified, and full. Note: A cylinder choke produces a very wide shot dispersion, whereas a full chose will provide a much tighter shot pattern. Different chokes are used for skeet, trap, and sporting clays. In hunting, the type of game and conditions will determine choke type.


CARBINE: A rifle of short length and light weight originally designed for horse-mounted troops.


CARTRIDGE: A single round of ammunition consisting of the case, primer, propellant, powder, and one or more projectiles.


CARTRIDGE, CENTERFIRE: Any cartridge intended for use in rifle, pistols, and revolvers that it has its primer central to the axis at the head of the case. Note: Most cartridges, including shotshells, are centerfire with the exception of 22 caliber rimfire ammunition. If you were to look at the bottom of a centerfire cartridge, you would see a small circle in the middle of the base, hence, "centerfire." There are a few rimfire ammunition calibers besides the 22, but they are rare and not widely available.


CARTRIDGE, MAGNUM: Any cartridge or shotshell that is larger, contains more shot, or produces a high 46 velocity than standard cartridges or shotshells of a given caliber or gauge.


CARTRIDGE, RIMFIRE: A cartridge containing the priming mixture in the rim of the base, usually a 22.


CARTRIDGE, SMALL BORE: A general term that refers to rimfire cartridges. Normally 22 caliber ammunition used for target shooting, plinking, and small game hunting.


CHAMBER: In a rifle, pistol, or shotgun, it is the part of a barrel that accepts the ammunition. In a revolver, it refers to the holes in the cylinder where the cartridges are loaded. The rear part of the barrel that is formed to accept the cartridge to be fired. A revolver employs a multi-chambered rotating cylinder separated from the stationary barrel.


CLIP: A device for holding a group of cartridges. Semantic wars have been fought over the word, with some insisting it is not a synonym for "detachable magazine." For 80 years, however, it has been so used by manufacturers and the military. There is no argument that it can also mean a separate device for holding and transferring a group of cartridges to a fixed or detachable magazine or as a device inserted with cartridges into the mechanism of a firearm becoming, in effect, part of that mechanism.


COCK: To place the hammer, or striker, in position for firing by pulling it back fully.


COMPENSATOR: A kind of muzzle brake, which diverts powder gases upward to reduce the upward recoil.


CORDITE: A British type of smokeless power made in long thin cords. Often encountered in fiction as "the smell of cordite." No longer in production.


CORROSIVE: Refers to a primer which contains potassium chlorate.


CYLINDER: The round, rotatable part of a revolver that contains the cartridge chambers. The drum of a revolver that contains the chambers for the ammunition.

 

D


DAMASCUS: A kind of rifle or shotgun barrel used until the late 19th century, made by a process giving a beautiful finish but insufficient strength for modern cartridges.


DERRINGER: A small single-shot or multi-barreled (rarely more than two) pocket pistol.

 A generic term referring to many variations of pocket-sized pistols. The name comes from the pistol's original designer, Henry Derringer. Note: According to the American Derringer Company, Henry Deringer's name is spelled with one 'R.' The proper spelling of Derringer firearms is with two 'R's.


DETONATE
: To explode with great violence. It is generally associated with high explosives e.g. TNT, dynamite, etc., and not with the relatively slow-burning smokeless gunpowders that are classed as propellants.


DISCHARGE: To cause a firearm to fire.


DISCONNECTOR: The part of a semiautomatic firearm, which prevents a second cartridge being fired until the trigger has been released and pulled again.


DOUBLE-ACTION: A handgun mechanism where pulling the trigger retracts and releases the hammer or firing pin to initiate discharge.


DOUBLE BARREL: Two barrels on a firearm mounted to one frame. The barrels can be vertically (over-under) or horizontally (side-by-side) aligned.


DRILLING: A three-barreled firearm, primarily European, with both rifle and shotgun barrels.


DUMDUM: See BULLET; DUMDUM. An early form of expanding bullet made at Dumdum Arsenal, India, in the 1890s, in an attempt to make the small bullets used in modern rifles as effective as the much larger and heavier bullets used with black powder muskets. A British military bullet developed in India's Dum-Dum Arsenal and used on India's North West Frontier and in the Sudan in 1897 and 1898. It was a jacketed .303 cal. British bullet with the jacket nose left open to expose the lead core in the hope of increasing effectiveness. Improvement was not pursued, for the Hague Convention of 1899 (not the Geneva Convention of 1925, which dealt largely with gas warfare) outlawed such bullets for warfare. Often "dum-dum" is misused as a term for any soft-nosed or hollow-pointed hunting bullet.

E


EXPLODING BULLET: A projectile containing an explosive component that acts on contact with the target. Seldom found and generally ineffective as such bullets lack the penetration necessary for defense or hunting.


EXPLOSIVE: Any substance (TNT, etc.) that, through chemical reaction, detonates or violently changes to gas with accompanying heat and pressure. Smokeless powder, by comparison, deflagrates (burns relatively slowly) and depends on its confinement in a gun's cartridge case and chamber for its potential as a propellant to be realized.

F


FIREARM: An assembly of a barrel and action from which is projectile is propelled as a result of combustion. Generally, a 'gun' carried and used by one person; but note that US legal definitions are variable and inconsistent. A rifle, shotgun or handgun using gunpowder as a propellant. By federal definition, under the 1968 Gun Control Act, antiques are excepted. Under the National Firearms Act, the word designates machine guns, etc. Airguns are not firearms.


FIRING PIN: The part of a firearm that strikes the primer cartridge to start the ignition of the primer.


FIXED AMMUNITION: A complete cartridge of several obsolete types and of today's rimfire and center-fire versions.


FLASH HIDER/FLASH SUPPRESSOR: A muzzle attachment intended to reduce visible muzzle flash caused by the burning propellant.

 An attachment to the muzzle designed to reduce muzzle flash. Note: A flash suppressor is not a silencer.


FREE RIFLE, FREE PISTOL: A firearm designed solely for extreme accuracy in 'international' target shooting.


FULL COCK: The position of the hammer when the firearm is ready to fire.

G


GAUGE: A term used to identify most shotgun bores, with the exception of the .410 shotgun. It relates to the number of bore diameter lead balls weighing one pound. Note: the .410 shotgun is a caliber. The .410 refers to the diameter of the barrel.

•    10 gauge - .775 inch
•    12 gauge - .730 inch
•    16 gauge - .670 inch
•    20 gauge - .615 inch
•    28 gauge - .550 inch
•    67 gauge - .410 inch


GROUP: A series of shots fired at the target used to adjust the sights or determine the accuracy of a firearm.

H


HALF-COCK: Hammer position, held away from the primer but with not enough spring compression to fire the primer if the hammer should fall. Pulling the trigger should not drop the hammer. (Source of the phrase "go off half-cocked").


HANDGUN: Synonym for pistol.


HANDLOADING: The process of putting a fresh primer, powder charge, and bullet into a used brass cartridge case (the most expensive part).


HANGFIRE: Perceptible delay between hammer or firing pin impact and actual firing.


HEADSPACE: The space available for the cartridge between the face of the breechblock and the part of the chamber that keeps the cartridge from going forward. A critical dimension.


HIGH-CAPACITY MAGAZINE: An inexact, non-technical term indicating a magazine holding more rounds than might be considered "average."


HOLLOW-POINT BULLET: A bullet with a concavity in its nose to increase expansion on penetration of a solid target.


HALF COCK: The position of the hammer about half retracted and intended to prevent release of the hammer by a normal pull of the trigger.


HAMMER: The part of the firing mechanism that strikes the firing pin, which, in turn, strikes the primer.


HAMMERLESS: A firearm having an internal hammer or striker.

J


JACKET: The envelope enclosing the core of a bullet.


JAM: A malfunction that prevents the action from operating. Jams may be caused by faulty or altered parts, ammunition, poor maintenance of the firearm, or improper use of the firearm.


JUMP: The upward and rearward recoil of a firearm when it is fired. It is commonly called recoil or "kick."

L


LANDS: The uncut surface of the bore of a rifled barrel.


LEVER-ACTION: A gun mechanism activated by manual operation of a lever.


LOAD: The combination of components used to assemble a cartridge or shotshell. The term also refers to the act of putting ammunition into a firearm.

M


MACHINE GUN: See ACTION, AUTOMATIC.


MACHINE GUN: Generally, an automatic weapon with ammunition fed from a belt, mounted on a tripod for firing from a fixed position. Early machine guns had water-cooled barrels, but essentially all now are air-cooled. 'Heavy' machine guns were water-cooled; 'light' ones were air-cooled. Some air-cooled machine guns are mounted on bipods for better mobility (less weight). The term is also often used generically for other automatic weapons.

A firearm of military significance, often crew-served, that on trigger depression automatically feeds and fires cartridges of rifle size or greater. Civilian ownership in the U.S. has been heavily curtailed and federally regulated since 1934.

An 'automatic rifle' is generally a rifle designed to fire automatically from a 'box magazine' holding perhaps 20 cartridges. It usually can be fired from a bipod or from the shoulder or waist, and generally uses 'full-power' cartridges (a distinction from an 'assault rifle'). The best US example is the Model 1918 Browning Automatic Rifle (BAR).

A submachine gun fires pistol cartridges, usually with blow-back action, and is designed to be highly portable.

Use dictionaries and glossaries with particularly great care on this subject!


MAGAZINE: A receptacle on a firearm that holds several cartridges or shells for feeding into the chamber. Magazines take many forms, such as box, drum, rotary, or tubular and may be fixed or removable.

A spring-loaded container for cartridges that may be an integral part of the gun's mechanism or may be detachable. Detachable magazines for the same gun may be offered by the gun's manufacturer or other manufacturers with various capacities. A gun with a five-shot detachable magazine, for instance, may be fitted with a magazine holding 10, 20, or 50 or more rounds. Box magazines are most commonly located under the receiver with the cartridges stacked vertically. Tube or tubular magazines run through the stock or under the barrel with the cartridges lying horizontally. Drum magazines hold their cartridges in a circular mode. A magazine can also mean a secure storage place for ammunition or explosives.
 The part of a repeating (including semiautomatic and automatic) firearm that holds cartridges for use. In the magazine, a spring forces cartridges into position to be fed into the chamber by operation of the action. In many firearms, the magazine is an integral part. In others, separate magazines, each  with its own spring, fit into the 'magazine well.' Those separate magazines are often incorrectly called 'clips'. A clip is either: (a) a device which holds a set of cartridges and is inserted as a whole into the magazine as in the US M1 rifle, or (b) a device which holds a set of cartridges which are pushed by the shooter into the magazine, as in the US M1903 Springfield rifle. This kind of clip is also a 'charger.'


MAGNUM: See CARTRIDGE, MAGNUM. A term indicating a relatively heavily loaded metallic cartridge or shotshell and, by extension, a gun safely constructed to fire it.


MERCURIAL: Refers to a primer composition containing a mercury compound. Non-mercurial primers are desired because traces of mercury in a fired cartridge case make it brittle and less useful for reloading.


MIL: Angular change in aim that moves the point of impact of an artillery projectile one meter at a range of 1000 meters.


MINUTE OF ANGLE (MOA): In this context, angular change in aim that moves the point of impact of a rifle bullet one inch at 100 yards; only approximately a true mathematical minute of angle.


MISFIRE: A failure of the cartridge to fire after the primer has been struck by the firing pin.


MULTI-BARRELED
: A gun with more than one barrel, the most common being the double-barreled shotgun.


MUSHROOMED BULLET
: A description of a bullet whose forward diameter has expanded after penetration.


MUZZLE: The front end of a firearm barrel from which the bullet or shot emerges. The open end of the barrel from which the projectile exits.


MUZZLE BRAKE: An attachment to or integral part of the barrel intended to trap and divert expanding gases and reduce recoil. An attachment to the muzzle which diverts powder gases backward to reduce recoil.


MUZZLE FLASH: The illumination (flash) resulting from the expanding gases from the burning propellant particles emerging from the barrel behind the projectile and uniting with oxygen in the air.


MUZZLE LOADER: The earliest type of gun, now also popular as modern-made replicas, in which blackpowder and projectile(s) are separately loaded in through the muzzle. The term is often applied to cap-and-ball revolvers where the loading is done not actually through the muzzle but through the open ends of the cylinder's chambers.
 Any firearm loaded through the muzzle. Also called "black powder" firearms. They may be antique, replica, or of modern design.

N


NOSE: The point or tip of a bullet.

O


OVER AND UNDER: A firearm with two barrels, one above the other.

P


+P AMMUNITION: The term "+p" refers to ammunition, which is loaded to a pressure level above the normal SAAMI specification. The term "+p" is a recognized SAAMI specification (e.g., 9mm+p, .45ACP+p). The term +p+, used only in reference to 9mm ammunition usually, refers to a round loaded beyond any SAAMI specifications. Most NATO-spec ammunition tends to be +p+. By manufacturing ammunition to a higher pressure level, companies can achieve greater velocity with any given bullet. This means more momentum and muzzle energy, but usually an increase in recoil and muzzle flip as well (particularly in .45ACP +p). There is no SAAMI specification for "+p+" ammunition. There are no SAAMI specifications for “+p” in 40S&W, 380ACP, 357SIG and 10mm.


POWDER, BLACK: The earliest type of propellant, allegedly made by the Chinese or Hindus. First used for firearms in the 13th century, it is a mechanical mixture of potassium or sodium nitrate, charcoal, and sulfur. It makes a large cloud of smoke when fired.


POWDER, SMOKELESS: A modern propellant containing mainly nitrocellulose or both nitrocellulose and nitroglycerin. Relatively little smoke is created when fired.


PRESSURE: The force developed by the expanding gases generated by the combustion of the propellant.


PRIMER: The ignition component consisting of brass or gilding metal cup, priming mixture, anvil, and foiling disc. It creates a spark when hit by a firing pin, igniting the propellant powder. The ignition component of a cartridge, generally made up of a metallic fulminate or (currently) lead styphnate.


PROPELLANT: The chemical composition which, when ignited by a primer, generate gas. The gas propels the projectile. See also POWDER.


PROOF: Used in the German sense of test (Prüf) (but the German word for it is 'Beschuss'). Testing a firearm with a particularly heavy charge to make sure that the firearm is strong enough for use.


PROPELLANT: In a firearm the chemical composition that is ignited by the primer to generate gas. In air or pellet guns, compressed air or CO2.


PYRODEX: A trade name for a blackpowder substitute, the only such safe substitute known at this time.

R


RECEIVER: The basic unit of a firearm which houses the firing mechanism and to which the barrel and stock are assembled. In revolvers, pistols and break-open firearms, it is called the frame. The housing for a firearm's breech (portion of the barrel with chamber into which a cartridge or projectile is loaded) and firing mechanism.


RECOIL: The rearward movement of a firearm resulting from firing a cartridge or shell.


RECOIL PAD: A butt plate, usually made of rubber, to reduce the recoil or "kick" of shoulder firearms.


RELOAD: A round of ammunition that has been assembled using fired cases. Note: Reloading is very popular among recreational target shooters, competitive shooters, and hunters. In addition to being cost-effective, reloading enables shooters to develop ammunition specifically designed for particular shooting disciplines or games.


REVOLVER: A firearm with a cylinder having several chambers so arranged as to rotate around an axis and be discharged successively by the same firing mechanism. A semi-automatic pistol is not a revolver because it does not have a revolving cylinder. A gun, usually a handgun, with a multi-chambered cylinder that rotates to successively align each chamber with a single barrel and firing pin.


RIFLE: A shoulder gun with rifled bore.

 A firearm having spiral grooves in the bore and designed to be fired from the shoulder. By law, rifle barrels must be at least 16" long. Handguns usually have rifled barrels as well.


RIFLING: Grooves formed in the bore of a firearm barrel to impart rotary motion to a projectile. Spiral grooves in a gun's bore that spin the projectile in flight and impart accuracy. Rifling is present in all true rifles, in most handguns and in some shotgun barrels designed for increasing the accuracy potential of slugs (a slug is a single projectile rather than the more common "shot.")


RIMFIRE: A rimmed or flanged cartridge with the priming mixture located inside the rim of the case. The most famous example is the .22 rimfire. It has been estimated that between 3-4 billion .22 cartridges are loaded in the U.S. each year.


ROUND: Synonym for a cartridge. One complete small arms cartridge.

S


SABOT: A lightweight carrier surrounding a heavier projectile of reduced caliber, allowing a firearm to shoot ammunition for which it is not chambered. For example, a hunter could use his .30-30 deer rifle to shoot small game with .22 centerfire bullets.


SAFETY: A device on a firearm designed to provide protection against accidental or unintentional discharge under normal usage when properly engaged.


SATURDAY NIGHT SPECIAL: A catchy phrase having no legal or technical meaning.


SAWED-OFF SHOTGUN (RIFLE) : Common term for federally restricted "short-barreled shotgun" (rifle) i.e. a conventional shotgun with barrel less than 18" (rifle less than 16") or overall length less than 26."


SELECTIVE-FIRE
: A firearm's ability to be fired fully automatically, semi-automatically or, in some cases, in burst-fire mode at the option of the firer.


SEMI-AUTOMATIC: Firearm which fires, extracts, ejects, and reloads only once for each pull and release of the trigger. A firearm designed to fire a single cartridge, eject the empty case and reload the chamber each time the trigger is pulled.


SHOTGUN: A smooth bore shoulder firearm designed to fire shells containing numerous pellets or a single slug. A shoulder gun with smooth-bored barrel(s) primarily intended for firing multiple small, round projectiles, (shot, birdshot, pellets), larger shot (buck shot), single round balls (pumpkin balls) and cylindrical slugs. Some shotgun barrels have rifling to give better accuracy with slugs or greater pattern spread to birdshot.


SHOTSHELL: A round of ammunition containing multiple pellets for use in a shotgun. The multiple pellets in a shotshell are called SHELL. The cartridge for a shotgun. It is also called a "shell," and its body may be of metal or plastic or of plastic or paper with a metal head. Small shotshells are also made for rifles and handguns and are often used for vermin control.


SILENCER: A device attached to the muzzle of a firearm to reduce the noise of discharge. Silencers are virtually prohibited for civilian ownership and use. A virtually prohibited device for attachment to a gun's muzzle for reducing (not silencing) the report. Better terms would be "sound suppressor" or "sound moderator."


SINGLE-SHOT: 
A gun mechanism lacking a magazine where separately carried ammunition must be manually placed in the gun's chamber for each firing.


SKEET: A clay target shooting sport with a shotgun. Shooters fire at clay targets crossing in front of them. Competitive shotgun shooting at 'clay pigeons' thrown from two different locations.


SKEET GUN: A shotgun with an open choke specifically designed for clay target skeet shooting or close range hunting.


SLIDE-ACTION
: A gun mechanism activated by manual operation of a horizontally sliding handle almost always located under the barrel. "Pump-action" and "trombone" are synonyms for "slide-action."


SNIPING: Military shooting at specific enemy personnel at long range, typically 400-1000 meters. The term is commonly misused in the US media.


SNUB-NOSED: Descriptive of (usually) a revolver with an unusually short barrel.


SPORTING CLAYS: Often called "golf with a shotgun," it is a sport in which shooters, using shotguns, fire at clay targets from different stations on a course laid out over varying terrain.


STOCK: The wood, fiberglass, wood laminate or plastic component to which the barrel and receiver are attached.


SUBMACHINE GUN: An automatic firearm commonly firing pistol ammunition intended for close-range combat.

T


TARGET, CLAY: A circular, domed frangible disc used as an aerial target for shotgun shooting games. Originally formed out of clay, modern targets are combination of pitch and limestone. Dimensions and weights are regulated by trap and skeet shooting associations. They are often called "clay pigeons."


TEFLON: Trade name for a synthetic sometimes used to coat hard bullets to protect the rifling. Other synthetics, nylon for instance, have also been used as bullet coatings. None of these soft coatings has any effect on lethality.


TELESCOPE SIGHT: An optical sight, which shows the shooter a magnified image of the target, with an indication (cross-hairs, for instance) of the point of aim. Because that display is in a single plane, a 'scope' sight does not require the shooter's eye to focus on both the front sight and the target at the same time – particularly useful for anyone above middle age.


TRAJECTORY: The path of a bullet through the air.


TRAP: A clay target throwing device, either power or hand-operated.


TRAP SHOOTING: A clay target shooting sport with a shotgun. Shooters fire at clay targets flying away from them. Shooters stand behind the trap at a distance from 16 to 27 yards. Competitive shotgun shooting at 'clay pigeons' thrown from a single location.


TRIGGER, HAIR: A slang term for a trigger requiring very low force to actuate. Note: Hair triggers are frequently used on a competitive target rifles and pistols for increased accuracy. The reduced force needed to pull the trigger allows the shooter's firearm to remain steady.


TRIGGER LOCK: An accessory for blocking a firearm from unauthorized use. Most trigger lock manufacturers advise against the use of a trigger lock on a loaded firearm, as shifting the lock against the trigger could fire the gun.


TRIGGER PULL: The average force which must be applied to the trigger to cause the firearm to fire. Note: Typically, non-target mode-firearms have a minimum trigger pull of 3 pounds. Double action revolvers often have a long, heavy trigger pull of around 10 pounds.


TRIGGER WEIGHT: The force which must be applied to the trigger to fire; measured by hanging a weight on the trigger. It is typically around 4 pounds (2 kg) if the arm is cocked. About 12-18 pounds (5-8 kg) must be applied to cock a double-action pistol.


TWIST: (Drall) Pitch of rifling, expressed as one turn in a distance along the barrel.

U


UNLOAD: The complete removal of all unfired ammunition from a firearm.

V


VARMINT: Variant of 'vermin,' meaning small animal(s) considered pests and often not protected by game laws. They are not only small but very alert so that a hunter cannot get close. A "varmint rifle" is generally of small caliber (.22 - .25) but must be very accurate at 200-400 yards.


VELOCITY: The speed of a projectile at any point along its trajectory, usually listed in "feet per second."

W


WADCUTTER: A cylindrical pistol bullet with a completely flat nose; used in target shooting to make clean-cut holes which are easier to score.


WAD: A space device in a shotshell, usually a cup-formed plastic or paper discs, that separates the propellant powder from the shot.


WEAPON
: Webster defines it as "an instrument of offensive or defensive combat." Thus an automobile, baseball bat, bottle, chair, firearm, fist, pen knife or shovel is a "weapon," if so used.

Z


ZERO: To adjust sights for a specific range by firing several trial shots at that range.