This Glossary is not designed for the weapon aficionado, but for a writer who wants to know in plain English what a particular term or description commonly means.
Assault Weapon: A common descriptor of small, light weight rifles. Controversial in the sense that assault rifles were banned by law for several years, but are not at this moment. A specific list of weapons was associated with this definition and ban and its enforcement by the Bureau of Alcohol, Tobacco and Firearms ( more commonly referred to as the ATF). The list included the AR-15/M-16 and the AK-47 in all their versions.
ATF: The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is a principal law enforcement agency within the United States Department of Justice dedicated to preventing terrorism, reducing violent crime, and protecting our Nation. The men and women of ATF perform the dual responsibilities of enforcing Federal criminal laws and regulating the firearms and explosives industries.
Automatic Fire: When the trigger is pulled, the weapon continuously fires until all ammunition is depleted or the trigger is released. Various techniques that distinguish weapons manufacturers or designers divert a portion of the gas from the exploding powder to cycle the loading mechanism, ejecting the spent cartridge, then chambering and firing the next round.
Automatic Pistol: A very misleading term since those pistols usually identified as automatics fire in the semi-automatic mode. This category is used to differentiate a pistol that automatically ejects the empty case and reloads a round from a magazine into the chamber after the preceding round has been fired, from a revolver.
Automatic Weapon: A weapon designed to fire long bursts of fire in the automatic mode. Most are submachine guns or machineguns. A very few pistols and rifles have been modified to fire on automatic, often by illegal and unreliable modifications.
Belt: In WWI, and WWII era machineguns, the belt was a layered fabric strip that held a long line of bullets which the gun mechanism could automatically feed into the weapon's chamber by means of a rapidly cycling pawl (a finger-like piece that pushed or pulled the next round into the breech). In modern weapons the belt is a series of metal links that fills the same purpose, but become unlinked and fall apart once the fired bullet case is ejected.
Blowback: When a round is fired, the exploding gases push the bolt back, ejecting the fired case and chambering the next round. This technique was developed to quickly field in mass produced, cheap weapons using relatively low powered rounds, but is occasionally found on modern, quality weapons. The other common system uses a recoil driven mechanism that uses a portion of the gas created by the explosion of the round to cycle the mechanism.
Bolt: The moveable mechanism in an automatic or semi-automatic weapon that pushes the bullet forward into the firing chamber. The face of the bolt locks into the breech and holds the round secure as the firing pin strikes the primer, firing the round. The bolt incorporates the ejector which pulls the empty case out of the chamber.
Break-action: All older single shot and double barrel (side-by-side and over-and-under) shotguns use a lever, either beside the hammer or incorporated into the trigger guard that allows the gun to be "broken" to load in a new shell.
Breech: The mouth or end of the barrel where the round is fed into the chamber, usually fitted with some form of locking mechanism to hold the bolt secure while the round is fired.
Bullet: The projective that fires out of the cartridge. The term is also often incorrectly used to describe the entire round. Bullets traditionally were molded lead, but in the early Twentieth Century many were coated in copper, leading the the term FMJ - full metal jacket - which now describes many common bullets. To improve their stopping power, bullets were modified with blunt points that led to other sophisticated designs that mushroom upon impact, creating much more lethal - or at least better stopping power - wounds.
Burst Fire: The weapon is designed to fire a burst, commonly three rounds, at each pull of the trigger, a compromise between automatic and semi-automatic fire. The intent is to improve the probability of a hit while economizing on the use of ammunition.
Caliber: Commonly indicates the diameter of the bullet, e.g. .45 caliber, which is a bullet .45 inches in diameter. The description may also include a number which indicates the total cartridge length, an indication of the amount of powder and therefore power, e.g. 6.5x55mm - a Swedish Mauser round that is 6.5mm in diameter and 55mm long, or a unique descriptor, e.g., .30/06 - a .30 caliber bullet adapted by the US army in 1906 for a series of military rifles.
Cartridge: The complete assembly encompassing a case, primer, powder and bullet. The term is used to describe the entire round. In common use, the term "bullet" is often incorrectly used to describe the complete assembly.
Case: Commonly a brass case used to hold the bullet, powder and primer. The case may be fabricated from some other alloy which may look silver in appearance.
Centerfire: Cartridges that are fired when the firing pin strikes a separate primer inserted in the center of the case base. This construction is used on the majority of ammunition available, in contract to various calibers of rimfire ammo.
Chamber: The end of the barrel where the bullet is inserted and held in place by the bolt or the receiver while the round is fired.
Class III: Class III weapons are fully automatic or suppressors (silencers in the old movie jargon).You may only own a machine gun that was manufactured and registered with the BATF before May 19, 1986. Weapons manufactured after that date are restricted for Military and Law Enforcement use only. A special fee and extensive paperwork filed with the BATF are required to purchase and own a Class III weapon.
Clip: A simple holder for bullets that allow a collection of bullets to be loaded at one time. A typical example (and one of the few that was ever in wide use for rifles) is the M1 Garand clip which holds eight rounds and ejects with a distinctive metallic clang after the last round is fired. When the clip is intended to be inserted in the weapon magazine with the rounds and ejected after the rounds are all fired, the correct term is "en-bloc" clip, but this term is very seldom used by anyone other than a weapon expert. A "moon clip" is a circular piece holding the rounds for a revolver in place, ready to be quickly inserted in the revolver cylinder. "Half-moon" clips are used to hold a cluster of rounds to insert in one half of a revolver cylinder. The term "clip" is often used by mistake, when the correct term for the part that holds bullets for most modern guns is "magazine." Also see "stripper clip."
Cylinder: The round revolving device that holds the bullets to be fired in a revolver and the empty cases that have already been fired.
Double Action Trigger: Pulling back a double action trigger activates a series of events: first cocking the hammer, then releasing the hammer to fall and fire the round in the chamber. In a modern revolver, the first stage of the trigger pull also rotates the cylinder holding the bullets and places the next bullet in position under the hammer ready to fire. In a modern automatic pistol, pulling the trigger cocks the hammer back and drops the hammer, firing the round, ejecting the spent case and loading the next round. Generally, a double action trigger pull is long and hard, a safety feature required by many law enforcement and military organizations. The result is a weapon that is considered by some to be safer, but is inherently less accurate for most shooters. Both double and single action pistols require both hands to load and fire the first round from an unloaded position, one to hold the pistol grip and a second to rack the receiver back to chamber the first round and cock the hammer. Certain special organizations teach the very difficult maneuver of operating the slide to load/reload with only one hand. Once cocked with a round in the chamber, a double action pistol will continue to fire, eject and load the next round with each pull of the trigger. If this is the only way a pistol can be fired, the manufacturer may describe this as a DAO (double action only) trigger. In comparison, see single action.
Double Stack: Describes a magazine that allows the bullets to "stack" in a staggered alignment, resulting in a wider magazine (requiring a wider grip) that holds more rounds. Common smaller pistols can hold up to twelve rounds, doubling the single stack version. Larger pistols can hold up to seventeen rounds - so don't count to six and assume the bad guy is out of ammo! Alternatively, see single stack.
Ejector: The ejector forces a case that has been removed from the breech out of the way of the bolt or receiver so a new round can be inserted. This is the mechanism that throws a spent case (or unfired round) out of a weapon when the action is cycled. The ejector may be a simple pin or obstruction that catches the extracted case using the rearward momentum of the case to flip it out of an automatic or semi-automatic weapon. Revolvers commonly have a rod protruding under the pistol barrel that can be manually pushed back, ejecting the empty cases from the revolver cylinder so it can be reloaded. Different weapon manuals often mix the terms and part nomenclatures for ejectors and extractors. Extraction is the action to remove a case from the breech of a weapon. Ejection is the subsequent action to eject a case from the weapon. These actions are linked, but usually have separate parts for the two consecutive actions.
Extractor: A mechanism in the action of an automatic or semi-automatic weapon or the breech of a single shot weapon that pulls the empty case from the chamber. The extractor may be a simple protuberance that snags an empty cartridge or shell case and pulls it from the chamber. Break action shotguns like the Tamer have a spring loaded extractor that pops the shell out of the breech when the gun is opened. In very old guns the spent cartridge or shell must be pulled out by hand due to either an absent (by design) or malfunctioning extractor or the extractor my by design only bring the spent shell out far enough to be grasped and manually removed.
Firing Pin: The small pin that is struck by the hammer and drives into the primer, set in the cartridge case, igniting the powder and firing the round.
Gauge: The size of a shotgun barrel bore and the appropriate shotgun shell that will fire in the gun, for example the most common bore is a 12 gauge barrel where the inside diameter is about three-quarters of an inch in diameter. The smallest commonly found shotgun round is the .410, which is .41in. in diameter, then the 20 gauge, commonly used in bird hunting, then the 16 gauge, not commonly made for modern arms but often found hiding in a closet corner. Rare 10 and even 8 gauge shotguns, originally designed for commercial migratory bird hunters, can be found, probably with more antique value than practical use. A very few 10 gauge guns are currently being manufactured.
Hammer: A lever on the rear of the weapon that must be mechanically or manually cocked back in preparation for firing. On most pistols and older rifles, this lever is often a visible mechanism. On many modern weapons the hammer is enclosed and not visible.
Magazine: A metal or plastic device designed to hold the bullets to be fed primarily into a semi-automatic weapon. In a pistol the magazine is fed into the grip and contains a spring that pushes a bullet follower which in turn feeds the bullets up so it can be grabbed but the bolt (in a rifle) or receiver (in a pistol) as it moves forward in the loading cycle. A poorly manufactured or damaged magazine can cause a miss-feed in a semi-automatic weapon. Older (WWI and WWII, AK and initial M16 series rifles and submachine guns also use magazines rather than belts.
NICS: Mandated by the Brady Handgun Violence Prevention Act (Brady Act) of 1993, Public Law 103-159, the National Instant Criminal Background Check System (NICS) was established for Federal Firearms Licensees (FFLs) to contact by telephone, or other electronic means, for information to be supplied immediately on whether the transfer of a firearm would be in violation of Section 922 (g) or (n) of Title 18, United States Code, or state law. The Brady Act is a public record and is available from many sources including the Internet at www.atf.treas.gov.
Percussion cap: A sensitive cap, historically filled with fulminate of mercury, that is struck by the hammer of a percussion weapon, sending a spurt of flame down to ignite the black powder packed behind the ball and patch of a black powder weapon. This technique is still used by rifles, pistols and even cannon.
Ported Weapon: Lightweight pistols firing powerful loads are harder to control than a heavier pistol. One option is to port the pistol, which is the drilling of two or three holes in the barrel and receiver, or the use of factory slots cut in the barrel. As the weapons fires, part of the energy that would normally contribute to felt recoil vents through the holes, reducing felt recoil and the weapon's inclination to kick up. The reduced recoil also means reduced velocity of the fired bullet - another contentious area to gun enthusiasts inclined to argue both sides.
Primer: The very sensitive charge set in the base of a cartridge
Receiver: The upper portion of a weapon that flies back in the recoil step of firing, functioning as a bolt. Important distinction: most semiautomatic pistols do not have a bolt. The receiver fulfills the same function. On a rifle such as the AR-15 or M-16, the receiver actually incorporates a bolt. If you have the opportunity to use these terms, check the parts diagram to be sure you have it correct. On a rifle, the metal shell that houses the trigger group. This is the part that is serial numbered and is accountable in legal transfers.
Recoil: The majority of modern semi-automatic weapons function using a recoil-generated cycle, where a portion of the gases from the fired round are ported back through a tube to the bolt or receiver, where the force is used to cycle the weapon, ejecting the empty case, loading a new round, and sometimes cocking the weapons in preparation for firing.
Rimfire: Cartriges that are fired when the firing pin strikes and ignites the primer in the outer rim of the base of the casing, rather than a separate primer inserted in the center of the base. Rimfire calibers are usually lower power, such as the common .22 Long Rifle caliber used in the majority of rimfire weapons or the less common but popular .17 caliber or .22 magnum rounds.
Round: A complete cartridge with the projectile, case, primer and powder.
Safety: Most often a lever, commonly on the left side of the weapon that can be operated by the left thumb of a right handed shooter, that renders the weapon incapable of firing. Many modern weapons have safeties on both sides of the weapon for ambidextrous operation. Placing the lever in the safe position may block the firing pin, or in some positive way ensure the weapon will not fire. The M1911 and a few others also have a safety built into the grip requiring the pistol to held in a "standard" grip to fire. The M1911 also has a "half-cock" position, where the hammer is pulled half way back and clicked into a detent. The pistol can not be fired from this position, and is also protected from being inadvertently fired if the pistol is dropped of the hammer otherwise struck in some manner. Some pistols have no safety at all and simply rely on the trigger not being pulled. These pistols commonly have addition features that work to block the firing pin from striking the case, and firing the bullet, if the pistol is inadvertently dropped or struck, as do many modern M1911 varients.
Single Action Trigger: The old frontier revolver has a single action trigger. The shooter must manually cock the hammer back which also rotates a new cartridge in place, aligned with the barrel. This leaves the trigger ready to fire the round in the cylinder, often with a very light touch (a hair trigger). For an experienced shooter, this is adds to the weapon's accuracy and quickness in getting off the first round, but is a slower process if several rounds are to be fired. The military M1911 automatic requires the first round to be chambered by a manual cycling of the receiver, (the two-handed action loading process described to the double action trigger) but subsequent rounds fire as quickly as the shooter can pull the trigger. The difference is that the single action semi-automatic, after the first round, provides the cocking action as part of the recoil process, leaving the pistol ready to fire with a relatively light and short pull of the trigger, leading to higher accuracy for most shooters. The disadvantage is that if the pistol is to be loaded and fired from an unloaded state, or the round in the chamber fails to fire, the shooter must use two hands to manually cycle a new round from the magazine into the chamber and cock the pistol. Several manufacturers now offer a compromise that allows the trigger to re-cock simply by allowing the trigger to go forward. The trigger can then be pulled again without cycling the slide and allowing the shooter to attempt to fire the round in the chamber. Pistol mechanisms with this capability are described as having a singleaction/doubleaction (SA/DA) trigger.
Semi-automatic Fire: Pull the trigger and one round is fired. A separate trigger pull is required for each round.
Semi-automatic Weapon: The weapon's inner mechanism may prepare it for the next shot, but a separate pull of the trigger is required to fire each round. The single shot shotguns are good examples, although the classic Derringer pistol and double barrel shotguns use the same principle, with two barrels.
Single Shot: Only one round can be loaded and fired at the time. The empty shell or cartridge must be manually ejected and a new unfired round inserted to be refired.
Single Stack: A magazine that has the bullets stacked one above the other in a straight line. This is the "traditional" magazine used for years and is unaccountably the most reliable, but limits the number of rounds that can be held in the magazine without reloading, usually seven or eight. Alternatively, see double stack.
Shotgun Shell: In the context of a shotgun, the fiber hull (up to around the '50s), the container in which the explosive powder is packed, topped by a fiber wad and then loose lead shot. The shell is ignited when the firing pin strikes the primer which is in the brass base forming the base of the hull. Modern shotgun shells have replaced the cardboard hull with plastic and the fiber wadding separating the powder and shot with a plastic device, still called a wad, but functionally more of a cup that holds the shot column together as it travels down and exits the shotgun barrel. The outside diameter of the shell is usually described in gauge, although the one exception is the .410 shotgun, which is actually a caliber.
Shot: Shotguns traditionally were loaded with lead shot, but starting in the '70s, the lead has been replaced with other alloys in recognition of the environmental impact, specifically lead poisoning to wildlife and some domestic animals.
Stripper Clip: A strip of metal that holds a collection of bullets by gripping each bullet by the case base and holding the group in a line so they can be "stripped," or loaded into a magazine or the bullet well of a weapon. The most recognizable image is an anti-aircraft gun loader in the WWII scenes pushing 20mm rounds down into the gun's feeding mechanism.
Ghillie Suit: Comes from Ghillie, a variation of Gillie, a male attendant to a Scottish Highland Chief, or a fishing and hunting guide. Ghillie suits are a full camouflage garment used by law enforcement and military snipers for concealment
Revolver: A pistol where the bullets are loaded into a cylinder that revolves each time the weapon is cocked placing the next bullet in the cylinder under the firing pin and aligned with the barrel. Highly reliable but limited in number of rounds, revolvers are rapidly being replaced in most law enforcement and military organizations with semi-automatic pistols. Thousands still exist.