Basic Gun Terminology

ACTION: The working mechanism of a firearm. Various types of actions exist, including single-shots, multi-barrels, revolvers, slide or pump actions, lever-actions, rolling blocks, bolt-actions, semi-automatics, and fully automatics.  The action is the moving parts of a firearm that allow loading, firing, unloading and the ejection of the spent case.

AIRGUN: The airgun is not a firearm but a gun that uses compressed air or carbon dioxide (CO2) to propel a bb or pellet. Examples: BB gun, pellet gun, CO2 gun.  They typically come in .177 and .22 calibers.

AMMUNITION: This generally refers to the assembled components of a complete cartridge or round. 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). Muzzleloading firearms are loaded by individual component and that is not considered to be ammunition per se.  In addition, a muzzleloader is considered to be unloaded if there is no priming powder in the pan (Flintlock) or no percussion cap on the nipple, (Percussion).  Often you'll hear new shooters call ammunition cartridges 'bullets', when bullets are really only one of the components of a single round of ammunition.

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.  Let me clarify that a true assault rifle can fire automatically, like a machine gun.  The media has successfully reworked the meaning of "assault weapon" to mean semi-automatic rifles with removable magazines.  If you repeat a lie often enough, people who don't know the truth will just accept it.  I think Adolph Hitler said something like that.

ASSAULT WEAPON: Any weapon used in an assault (see WEAPON).  Get it, assault is a verb, not an adjective.

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 feeding 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.  A machine pistol is a different thing altogether.  When shooters refer to an automatic handgun, they are more than likely referring to a semi-automatic handgun and not a true machine pistol.

BALL: Originally a spherical projectile, now generally a fully jacketed bullet of cylindrical profile with a round or pointed nose. Most commonly used in military terminology.

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.  The basic recipe for black powder was put together by the Chinese just after the year 900 A.D.

BLANK CARTRIDGE: A round loaded with black powder or a special smokeless powder but lacking a projectile or bullet. Used mainly in starting races, theatrical productions, troop exercises and in training dogs.

BOLT-ACTION: A gun mechanism activated by manual operation of the breechblock that resembles a common door bolt.  The cartridge is loaded and unloaded by the use of this bolt.

BORE: The interior of a firearm's barrel excluding the chamber.  Bore is measured from land to land. (not from within the grooves)

BRASS: Another name for expended empty metallic cartridge cases.

BULLET: The projectile expelled from a gun. It is not synonymous with a 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.  The bullet is the only object that leaves the barrel.  Many unknowledgeable people refer to cartridges as bullets.

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.

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.  Most carbines are semi-automatic center-fire rifles with short barrels.  Semi-automatic carbines of 5.56mm and 7.62mm, are sometimes erroneously called 'assault rifles'.

CARTRIDGE: A single, complete round of ammunition consisting of the case, powder, bullet, and primer.  It can also mean a complete shotgun shell.

CASE, CASING: The metal 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: 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.  This rotating chamber rotates the live cartridge under the firing pin.

CHOKE: A constriction at or near the muzzle of a shotgun barrel that affects shot dispersion.

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.  In my opinion, a clip is not the same as a magazine, however, it seems that I have been overruled by the abuse of this term.

COP-KILLER BULLET: An inflammatory phrase having neither historical basis nor legal or technical meanings.  This is merely a media contrived term to gain a sensationalistic slant.

CYLINDER: The drum of a revolver that contains the chambers for the ammunition.

DERRINGER: A small single-shot or multi-barreled (rarely more than two) pocket pistol.  Although I have seen them with four barrels.

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 gun powders that are classed as propellants.

DOUBLE-ACTION: A handgun mechanism where pulling the trigger retracts and releases the hammer or firing pin to initiate discharge.  The trigger performs two functions, namely cocking the hammer and releasing the hammer.  Because the action in a double-action firearm performs two separate actions, it is called 'double-action'.

DUM-DUM BULLET: A British military bullet developed in India's Dum-Dum Arsenal and used on India's North West Frontier and in 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.

EXPANDING BULLET: A bullet that is specifically designed to increase in diameter upon entering a target. Almost all rifle bullets intended for hunting are intended to expand on impact.  Most hollow point bullets can be called expanding bullets.

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.  I know of no manufacturer that makes an exploding bullet.  The exploding bullet is really just a very rarely occurring myth.

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

FIREARM: 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. Air guns, pellet guns and/or bb guns are not firearms.

FIXED AMMUNITION: A complete cartridge of several 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.  These are used in the military to help conceal the shooting position in low light.

GAUGE: The bore size of a shotgun determined by the number of round lead balls of bore diameter that equals a pound.  For example, take one pound of lead, divide it equally into 12 spheres.  Each sphere would be 12 gauge in diameter.  Therefore, if you follow that definition it is easier to see why a 20 gauge shotgun is smaller in diameter than a 12 gauge shotgun.

GUN: The British restrict the term in portable arms to shotguns. Here it is properly used for rifles, shotguns, handguns, and air guns, as well as some cannons.

GUNPOWDER: Chemical substances of various compositions, particle sizes, shapes and colors that, on the ignition, serve as a propellant. Ignited smokeless powder emits minimal quantities of smoke from a gun's muzzle; the older black powder emits relatively large quantities of whitish smoke.  Modern smokeless gunpowder is made from nitroglycerin and nitrocellulose.

HANDGUN: Another name for a pistol or revolver.  The term handgun (actually handgonne) was first used in the year 1388.  Here is a picture of a handgun that has been dated very close to that era.  Firearms have been around since about the year 1245-1250 according to most historians who know their stuff.

HIGH-CAPACITY MAGAZINE: An inexact, non-technical term indicating a magazine holding more rounds that might be considered "average".  This term is usually used by individuals who don't know what they are speaking about.

HOLLOW-POINT BULLET: A bullet with a cavity in its nose to increase expansion upon penetration of a target.  There is much misinformation being bandied about by people with an alarming lack of knowledge about this subject.  Hollowpoint bullets are bullets that are merely designed with an empty cavity in its nose so that the diameter of the bullet increases slightly after it enters a target.

JACKET: The envelope enclosing the core of a bullet.  Usually made of copper and exists to help retain bullet weight throughout the penetration of a target.

LEVER-ACTION: A gun mechanism activated by manual operation of a lever.  The .30-30 rifle used on the Rifleman television show was a lever-action.

LIMP-WRISTING:  Limp-wristing a gun occurs only in semi-automatic and fully automatic handguns.  Limp-wristing occurs when the shooter does not hold the grip of the pistol strongly enough, allowing the handgun to recoil back into the hand.  When a shooter allows his/her wrist to flex too much or in other words, the shooter allows a very soft wrist, the handgun's recoiling slide will not gain enough inertia from the spent cartridge to completely cycle.  If the slide is not allowed a complete cycle, the spent casing will likely not be ejected properly and a fresh cartridge will likely not be stripped from the top of the magazine properly either.  If the shooter experiences jams, malfunctions, bad ejections and misfeeds in a semi-automatic pistol, limp-wristing could play a major role and it might not be entirely the fault of the firearm.

MACHINE GUN: 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.  Yet some machine guns are still used illegally because criminals typically disobey the law by nature.

MAGAZINE: 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.

MAGNUM: A term indicating a relatively heavily loaded metallic cartridge or shotshell and, by extension, a gun safely constructed to fire it.  Usually, a magnum cartridge is longer to hold more powder.

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 open end of the barrel from which the projectile exits.

MUZZLE BRAKE: An attachment to or an integral part of the barrel intended to trap and divert expanding gasses and reduce recoil.

MUZZLE LOADER: The earliest type of gun, now also popular as modern-made replicas, in which black powder 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.

PELLETS: Small spherical projectiles loaded in shotshells and more often called "shot." Also, the skirted projectiles used in air guns or pellet guns.

PELLET GUN: A rifle or pistol using compressed air or CO2 to propel a skirted pellet as opposed to a spherical BB. Not a firearm.

PISTOL: Synonymous with "handgun." A gun that is generally held in one hand. It may be of the single-shot, multi-barrel, repeating or semi-automatic variety and includes revolvers.

PISTOL GRIP: The handle of a handgun or protrusion on the buttstock or fore-end of a shoulder-operated gun that resembles the grip or handle of a handgun. A "semi-pistol grip" is one less pronounced than normal; a "vertical pistol grip" is more pronounced than normal.

PLINKING: Informal shooting at any of a variety of inanimate targets. The most often practiced shooting sport in this country.

PRIMER: The ignition component of a cartridge, generally made up of a metallic fulminate or (currently) lead styphnate.

PROPELLANT: In a cartridge, the chemical composition that is ignited by the primer to generate the superheated gas that propels the bullet from the barrel.  Propellants are usually made from some form of nitroglycerin and nitrocellulose.   In air or pellet guns, compressed air or CO2.  (see gunpowder)

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

RECEIVER: The housing for a firearm's breech (a portion of the barrel with the chamber into which a cartridge or projectile is loaded) and firing mechanism.

REVOLVER: A gun, usually a handgun, with a multi-chambered cylinder that rotates to successively align each chamber with a single barrel, hammer and firing pin.

RIFLE: A shoulder-fired gun with a rifled bore.

RIFLING: 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 fired in the U.S. each year.

ROUND: Another name for a single cartridge.  New shooters and people unfamiliar with firearms have sometimes been confused by the term 'round'.  They need not be confused any longer.  A 'round' is a single cartridge.  Instead of saying that 'I just fired a single shot at the target.'  You could say, 'I just shot one round'.

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.

SATURDAY NIGHT SPECIAL: A catchy phrase having no legal or technical meaning.  Normally this term is used by anti-Second Amendment types who know almost nothing about firearms.  Basically a sensationalistic term with no real meaning.  There was a song by Lynard Skynard that referred to a particular handgun as a 'Saturday Night Special', but no such firearm exists.  When people who have extremely limited firearm knowledge use the term, they are likely referring to very concealable and comparatively inexpensive semi-automatic pistols of .25 ACP caliber or even.380 ACP caliber, such as some models produced by Raven Arms and perhaps such off-shoots as Bryco, Jennings, and Davis.

SAWED-OFF SHOTGUN or (RIFLE): Common term for federally restricted "short-barreled shotgun or (rifle)" i.e. a conventional shotgun with a 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 shooter.  All selective-fire firearms are classified as Class III firearms and have been very heavily restricted, limited and taxed since the National Firearms Act of 1934.

SEMI-AUTOMATIC: A firearm that is designed to fire a single cartridge, eject the empty case and reload the chamber from an ammunition magazine of some type each time the trigger is pulled.

SHOTGUN: A shoulder-fired gun with smooth-bored barrel(s) primarily intended for firing multiple small, round projectiles, (shot, birdshot, pellets), larger shot (buckshot), single round balls and cylindrical slugs. Some shotgun barrels have rifling to give better accuracy with slugs or greater pattern spread to birdshot.

SHOTSHELL: 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 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."  Silencers are effective in reducing the sound created by a gunshot, but it is usually only effective if the ammunition is 'downloaded' so that the bullet does not break the sound barrier.

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

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."

SNUB-NOSED: Descriptive of (usually) a revolver with an unusually short barrel of say two inches or less.

SUB-MACHINE GUN: A fully automatic firearm commonly firing pistol ammunition intended for close-range combat.

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.

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


RA 10591 Comprehensive Firearms and Ammunition Regulation Act


Forensic Ballistics Reviewer