The Everything2 Gun Dictionary


This is by no means comprehensive... but you can help get it closer to being so! If you came here looking for a piece of firearms-related terminology, but didn't find it, let me know!

This dictionary concerns itself with modern small arms only - anything that pertains solely to wheel/flint/matchlocks, muskets, cannons, or artillery doesn't belong here.

Many thanks to The Custodian who helped scour the database for existing nodes prior to publishing, and everyone who has, or will, suggest entries!


+P, +P+: Designator on certain types of modern ammunition that denote it is loaded with a larger charge of powder than normal for that particular ammunition type. Popular for use in pistols meant for self-defense use, +P or +P+ cannot safely be used in weapons that are not specifically rated for it, even if they will physically fit into the chamber. See: Magnum

3-dot: Called a "3-dot" or sometimes "3-dot combat sight", a 3-dot sight has a contrasting (usually white or glow in the dark) dot, or sometimes triangle, on each of the rear notches and also the front post, as visible from the shooter's perspective. Found almost exclusively on handguns, they are meant to aid in rapid target acquisition, and to allow an aimed, though not precise, shot in minimal time. See: Open Sight


Action: The mechanism of a firearm directly behind the barrel, by which a gun is loaded, locked, fired, unlocked, extracted and ejected. Most commonly seen in the descriptive terms bolt action, single action, and double action.

Anvil: That part of the cartridge primer which is a solid surface, against which the firing pin strikes to set off the priming powder.

Autoloading: See: Semi-Automatic

Automatic: Can refer to the continuous firing of a machine-gun (See: Machine Gun), a mode of weapon fire on a select-fire weapon (See: Select-fire), or a semiautomatic pistol.


Ball: The spherical lead missile fired by smoothbore firearms. The term is used today when referring to some types of bullets fired from rifled barrels, e.g. .45 ACP Ball, sometimes called round-nose. Also refers to certain types of powder, e.g. Accurate Arms 2520 or Winchester WST See: Powder

Ballistic Coefficient: A number which indicates how a bullet's shape, length, weight, diameter and nose design affect its stability, velocity and range against air resistance.

Ballistics: The study of what happens to moving projectiles in the barrel and in flight - their trajectory, force, impact and penetration. "Internal ballistics" refers to what happens inside the barrel before the bullet or shot leaves the muzzle; "External ballistics" is what happens after the bullet or shot leaves the barrel and travels to its final point of impact and "terminal ballistics" is what happens to the bullet at the final point of impact.

Barrel: The metal tube of a firearm made from iron or steel, through which the bullet or shot charge passes when the firearm is fired.

Base Wad: The paper filler at the rear of the powder charge of the shotgun shell.

Battery: A term used to denote that the slide, bolt, or analogous part of the action is in position to fire, e.g. "Pressing the slide release lever will return the slide to battery."

Battlesight zero: A known amount of elevation and windage 'clicks' necessary to bring a mechanically centered set of sights into rough zero for a given shooter.

Bead sight: A type of sight commonly seen on shotgun barrels not specifically designed for slugs, the bead sight is a simple metallic or painted bead at the muzzle-end of the barrel. There is no rear sight, instead the shooter sights down the top of the barrel, sometimes using the top of the receiver as a reference.

Beavertail: A wide, flat fore-end of a rifle or shotgun. Or, more commonly, a style of tang on the upper part of a handgun grip.

Bedding: That part of the stock into which the action and/or barrel fits. Consists of one or several contours or cavities, and can be plain, or reinforced and custom fitted to a specific action. See: Inletting, Glass bedding

Belt: The narrow band around the rear section of a cartridge case just forward of the extractor groove. The belt arrests the progress of the case into the chamber and controls headspace.

Berdan Primer: The type of primer widely used outside of the US. Aside from structural differences, the most important factor is usually that Berdan-primed cases are extremely difficult to reload. See: Primer

Black Powder: A finely ground mixture of three basic ingredients - saltpeter (potassium nitrate), charcoal (carbon) and sulphur.

Blown Pattern: A shotgun pattern with erratic shot distribution, generally caused by gas escaping past the wads and getting into the shot.

Bluing: A process of treating metal gun parts. "True" bluing is an electrochemical passivation process which selectively converts the iron (Fe) of the surface of the piece to magnetite (Fe3O4). Bluing is not a 100% rust preventative - blued pieces should be very lightly oiled, including the exterior surfaces.

Boattail: The tapered rear end of a bullet. Also called "taper heel", this design is used to increase ballistic efficiency at long range.

Bolt: A steel rod-like assembly which moves back and forth in a bolt action, sealing the cartridge in the chamber during firing.

Bolt Face: The forward end of the bolt which supports the base of the cartridge and contains the firing pin.

Bore: The tunnel down the barrel of a firearm through which the projectiles travel.

Bore Diameter: The measurement from one side of the bore to the other. In a rifled barrel this means measurement of the bore before the rifling grooves are cut.

Boxer Primer: The type of primer system that is more prevalent in the US. Also called "reloadable primers". See: Primer

Breaching round: A sintered metal slug designed specifically for breaching doors. Usually fired from a shotgun, and from a distance of around 6 inches from the hinge or latch, it disintegrates into its component powder (usually copper dust) on impact. It is meant to transfer as much energy as possible into the target while producing no large shrapnel of its own.

Breech: The rear end of the barrel In modern arms, the portion of the barrel into which the cartridge is inserted. See: Chamber.

Breechblock: The part in the breech mechanism that locks the action against the firing of the cartridge.

Breechloader: A firearm loaded through the breech.

Buckshot: Large lead or metallic pellets used in shotshells, intended specifically for deer or other large game. Can include anything from #4 to #000.

Buffer: Inert powder used to fill empty space in a shotshell, both between the first wad and the shot cup, and also in the space between pellets inside the shot cup. Intended to improve shot patterning by limiting deformation of pellets during travel down the barrel.

Bullet: A single projectile fired from a firearm.

Butt: The rear end of a rifle or shotgun. The portion that rests against the shoulder.

Buttplate: A plate which covers the butt. Some steel buttplates have trap doors covering a recess for storage of cleaning equipment.


Caliber: The diameter of the bore of a rifle before the rifling grooves are cut. Usually expressed in decimal inches (.45) or millimeters (7.62).

Cannelure: A groove around the circumference of a bullet or case. For example, the lubrication grooves of lead bullets, or the grooves into which the mouth of the cartridge case is crimped, or the extractor grooves of the rimless or belted case.

Cant: To tilt or lean a gun to the side when aiming.

Cap: See: Percussion Cap.

Carbine: A light short-barreled riffle.

Cartridge: A case, usually made of brass, steel, or copper, containing the powder charge, the primer and the bullet. Before development of the metallic cartridge, the term was used to mean a roll or case of paper containing powder and shot. Modern cartridges are generally classified in three categories; centrefire metallics, rimfires, and shotshells. Centrefire metallics include all metal cartridges that have primers in the center of the base. Rimfires include all cartridges in which the priming powder is sealed in the soft rim around the base. Shotshells, often just called "shells", include all cartridges that contain shot, or small pellets, instead of a single bullet. Slug cartridges designed for shotguns are often called shells as well.

Center-Fire: See: Cartridge.

Chamber: The enlarged portion of the barrel at the breech in which the cartridge is placed ready for firing.

Checkering: A diamond-like patter on fore-ends and grips of firearms. The diamonds are made by cutting crossing lines into the material with special tools. Often described in "LPI", or Lines per Inch; higher LPI is a finer checkering.

Choke: The constriction at the muzzle of a shotgun barrel by which the spread of the shot pattern is controlled.

Clip: Also "stripper clip"; A metal, plastic, or sometimes fabric device used to hold ammunition in place for loading into (charging) a magazine, usually an internal magazine.

Closed Aperture Sights: A type of iron sights, the most common being peep sights. See respective entries for more details.

Closed bolt: A type of action which, when ready to fire, a round is in the chamber and the bolt and working parts are forward. Most modern firearms are of this type, due to the decreased chance of runaway fire due to a malfunction or part breakage.

Cock: To set the action into position for firing. On some firearms the action has an intermediate position called half cock.

Comb: The upper edge of a rifle or shotgun stock where the cheek rests.

Cone: The sloping portion at the front end of a shotgun chamber in which the chamber diameter is decreased to the diameter of the muzzle. Also, the rear portion of the choke at the muzzle of a shotgun.

Conical Bullet: A cone-shaped bullet.

Cordite: A double-base smokeless powder made of nitroglycerine and guncotton which is used in the form of long, stringy cords.

Controlled feed: Also sometimes called a "three point action"; an action by which rounds are under positive control at all times; The benefit to a controlled feed is that the action will reliably function in all orientations - upside-down, sideways, etc. - at the cost of (usually) more complexity.

Core: The part of a bullet that is covered by a jacket, or, the penetrating rod in a lead penetrating bullet or slug.

Corrosion: The gradual eating away of the metal parts of a firearm caused by rust.

Creep: The movement of the trigger before it releases. Also called drag or crawl.

Crimp: The portion of a cartridge case that is bent inward to hold the bullet in place, or in the case of shotshell, to hold the shot charge in place.

Cross Hairs: The sighting lines in a telescopic sight. Also see reticule.


Damascus Barrels: Barrels made of strips of iron and steel welded together in a spiral fashion. Modern ammunition should not be used in such firearms.

Deterrent: A material added to an explosive to slow its burning rate.

Double-Base Powder: A rapidly burning powder made by absorbing nitroglycerine into nitrocellulose (guncotton). Cordite is a double-base powder.

Doughnut Pattern: A shotgun pattern with a hole in the middle generally caused by the interference of the top wad.

Down Range: The direction from the shooting position to the target on a range. See: Range.

Drift: The departure of a bullet or shot charge from the normal line of flight. This can be caused by wind or the unbalanced spinning of the bullet. May also refer to a "drift punch", a type of tool commonly used to drive pins in or out, or to adjust dovetailed sights.


Ejector: The mechanism which throws the cartridge case free from the gun. Usually a block or blade that is integral to the receiver or frame of the gun, and stationary relative to the movement of the slide or bolt.

Elevation: The degree of adjustment of a rear sight or scope reticule necessary to cause the bullet to strike higher on the target.

Energy: The amount of work done by a bullet, expressed in foot pounds.

Erosion: The wearing away of a barrel's metal surface by a bullet or shot charge, or by the heat of powder gases or corrosive residue.

Extractor: A hook device which pulls the case out of a chamber as the breech mechanism is opened. The extractor generally brings the case within reach of the ejector, which then flips or pushes it out of the action.


Feed: The action of moving live cartridges from the magazine of a firearm into the chamber.

Firing Pin: The part of the breech mechanism which strikes the primer of the cartridge. In most firearms, the firing pin is part of the bolt assembly.

Flash hider: Contrary to popular belief, the flash hider is not meant to disguise the muzzle blast from observers; it is intended to reduce the visible portion of muzzle blast from the shooter's perspective, reducing flash blindness.

Flinch: To move or jerk a firearm involuntarily while shooting. A reflex action often done in anticipation of recoil, it is one of the top causes of inaccurate shot placement.

Floor Plate: The detachable metal plate at the bottom of the cartridge magazine of a bolt action rifle. The floor plate is usually hinged at the front and held by a release spring located just ahead of the trigger guard.

Fore-End: The forward portion of a shoulder-arm stock. Located under the barrel, the fore-end serves as a hand-hold.

F.P.S. or FPS: Abbreviation for feet per second. A term used in expressing the velocity of a bullet.

Frame: See: Receiver


Gain Twist: Barrel rifling which increases in pitch from the breech to the muzzle to accelerate the spin of a bullet.

Gas Check: A metal cup placed on the end of a lead bullet to protect the lead against the hot gases of the burning powder charge.

Gas Port: A small hole in the barrel of a gas-operated firearm through which expanding gases escape to power the autoloading system.

Gage: Also "gauge"; Measurement of shotgun bores derived from the number of bore-sized balls of lead to the pound. For example, 12 balls which fit the bore of a 12-gauge shotgun weigh one pound.

Ghost ring: A type of sight seen most commonly on shotguns designed for combat use. The front and rear sights are a set of rings, the front slightly smaller, designed for rapid acquisition of the target in the sight picture. Not meant for precision shooting.

Glass bedding: Glass bedding is a method by which the bed of a stock (the area in which the action is mounted) is both reinforced, and molded perfectly to the action, with resin and/or fiberglass. Its primary purpose is to keep the action from shifting at all during operation or firing, increasing mechanical accuracy.

Grain or grains: A unit of measure most often used to describe the weight of a bullet and also the weight of the powder charge in the case. Roughly .065 grams.

Grip: The small portion of the stock gripped by the trigger hand.

Grip Cap: A cap fastened over the end of a pistol grip on a rifle or shotgun stock.

Grooves: See: Rifling.

Group: A series of shots fired with the same sight setting and the same point of aim.


Half Cock: See: Cock.

Hammer: The part of the action that drives the firing pin forward.

Hammerless: Refers to a firearm whose hammer and striker are concealed within the metal frame or slide.

Hangfire: Delay in firing a cartridge after the firing pin has struck the primer. Can be extremely dangerous if not handled appropriately.

Headspace: The distance between the base of the cartridge and the face of the bolt or breechlock. This is determined by the rim of rimmed cartridges, the belt of belted cartridges and the shoulder or rimless cartridges.

Heel: The rear end of the upper edge of a gunstock. Also the base of a bullet.

Holding: The action of keeping the sights on the target while applying pressure to the trigger.

Hollow Point: A bullet with a nose cavity designed to increase its expansion on impact.

Holographic sight: A type of red dot sight that uses a projected laser hologram instead of a red dot. These have the advantage of being parallax free in all parts of the reticle window.


Igniting Charge: The charge used to ignite the propelling charge. See: Primer.

Inertia Firing Pin: A firing pin which moves freely forward and backward in the breechblock. The striker impels it forward while the explosion of the primer impels it backward.

Inletting: The cavity in a stock's bedding into which the action and/or barrel are fitted and mounted. Also refers to the process by which the cavity is carved or otherwise formed. See: Bedding

Internal Ballistics: See: Ballistics.

Iron sights: A non-telescopic firearm sight. Can refer to bead, open or closed sights (refer to their respective entries for more information).


Jacket: The outer covering over the inner metal core of a bullet. Seen most often in abbreviations of ammunition type; JHP and FMJ stand for Jacketed Hollowpoint and Full Metal Jacket, respectively.

Jump: The amount of change in the bore axis, measured both vertically and horizontally, while the projectile moves from the chamber to the muzzle when it is fired.


Kentucky Windage: The practice of intentionally aiming off-center in order to correct for windage or elevation, rather than adjusting the sight. Used sometimes to correct point of impact when full range of adjustment of the sights has been exhausted, also to correct for the ballistic path of a bullet when shooting at a target closer or farther away than the zero distance. See: Windage, Zero

Keyholing: The failure of a bullet to remain balanced in flight so that it enters the target sideways, leaving an elongated opening, which resembles an old-fashioned keyhole.

Kick: The backward movement of a firearm generated by the discharge of the projectile. See: Recoil.

Knurled Surface: A metal surface which contains a pattern of ridges or beads. This rough surface aids grasping a metal part to move it.


Lands: In the rifling of a bore, the uncut portions of the barrel's inner surface left after the rifling grooves have been cut into the metal. See: Rifling.

Leading: Fouling of a firearm bore by metal particles from bullets adhering to the metal surface caused by heat or friction.

Lede: The bevelled portion of the rifling at the rear end of the barrel (and the forward portion of the chamber) where the bullet first engages the lands.

Length Of Pull: The distance from the front trigger of a shotgun to the center of the butt.

Lever Action: An action operated by a lever located underneath it. A secondary purpose of the lever is often to serve as a trigger guard.

Line Of Bore: An imaginary straight line through the center of the bore of a firearm extending to infinity.

Line Of Sight: An imaginary straight line from the eye through the sights of a firearm to the target.

Load: A charge of powder, a projectile or a cartridge. Also, to prepare a gun for firing by inserting ammunition into it, or to charge a magazine by inserting cartridges into it.

Loading Gate: The hinged cover over the opening through which cartridges are inserted into the magazine.

Lock: The firing mechanism of a a muzzle-loading weapon. In breech-loading firearms, the lock is the firing mechanism and breech-sealing assembly.

Locking Lugs: A series of projections on the bolt of a firearm designed to fit into corresponding slots in the receiver or slide to lock the action in closed position for firing.

Lock Time: The interval of time between trigger release and the detonation of the primer.

Lug: Any protrusion which is meant to impede the motion of, or lock in place, any moving piece, such as a bayonet lug, which is used to mount a bayonet, or breech lugs, which are meant to lock a barrel in place when the bolt or slide is in battery or while firing.


Machine Gun: A now-generic term for an automatic or select-fire weapon. Traditionally associated with a weapon meant to fire continuously until the trigger is released. In the US, the National Firearms Act has specific definitions for what constitutes a machine gun under US law; obtaining them is a difficult process in most cases. See: Select-fire, Automatic.

Magazine: The part of a repeating firearm which holds the cartridges or shells in position ready to be loaded one at a time into the chamber. The magazine may be an integral part of a firearm or a separate device attached to the action.

Magnum: A cartridge or shell with greater power than normal (i.e. .300 magnum rifle, 3 inch magnum shotshell). Care must be taken to not load magnum or +P rounds into a firearm not designed to handle them - they are often dimensionally similar or even identical to their non-magnum counterparts!

Mainspring: A strong spring which activates the striker or hammer of a firearm.

Mauser action: Any action which mechanically is a derivative of the G98 bolt-action military rifle, introduced in 1898. Also known as a "Mauser claw action" or a "Mauser controlled feed", it is one of the strongest, most reliable bolt actions ever built.

Metal Cased: A bullet with a lead core and a solid metal jacket. See: Jacket

Metallic Cartridge: A cartridge with a metallic case. (Early cartridge cases were made of linen, paper, etc.) A term not usually used except for particular emphasis, such as with a brass or copper shotgun shell (which are traditionally paper or plastic), as nearly all cartridges are now metallic.

Metallic Sight: See: Iron Sights

Mexican Match: Surplus ammunition that has been disassembled and altered in some way, usually for increased consistency. The term and practice have fallen out of use since the 1970s. See: Moscow Match

Mid-Range: The point in the trajectory halfway between the muzzle and the target. May also refer to the theoretical point of the parabola traveled by the bullet.

Misfire: Failure of a cartridge to discharge after the firearm's firing pin has struck the primer. Common with cheap rimfire ammunition. See: Hangfire.

Mouth: The open end of a cartridge case into which the bullet is inserted when loading or reloading ammunition.

Moscow Match: Surplus Soviet and former Soviet ammunition that has been disassembled and altered in some way, usually for increased consistency. Similar to Mexican Match.

Mushroom: The shape many bullets assume when the tip expands upon striking. Hollowpoint ammunition is specifically designed to mushroom as much as possible, in order to create a larger wound channel and maximize energy transfer from the bullet to the target.

Muzzle: The forward end of a barrel.

Muzzle Blast: The violent disturbance in the atmosphere after discharge of a firearm, caused by release of powder gases into the air.

Muzzle Brake: A slotted device attached to the muzzle which softens the kick of the firearm. Often appears to be similar to a flash hider, but with a different purpose.

Muzzle Energy: The energy of a bullet as it emerges from the muzzle. (Usually expressed in foot pounds.)

Muzzle Flash: The bright flash at the muzzle of a firearm resulting from burning of gases.

Muzzleloader: A firearm that is loaded through the muzzle, like a musket of old; however, almost all modern muzzleloaders have rifled barrels.

Muzzle Velocity: See: Velocity.


Naked Bullet: A bullet not covered by a metal jacket or patch. Also referred to as "lead" or "hardened lead" bullets, depending on the material used to cast them and their treatment after casting.

Neck: The forward portion of a bottlenecked cartridge case. Also the portion of a rifle chamber in which the neck of the cartridge case rests.

Night sight: Sights with light channeling fiber optic, or glow in the dark inserts. Available in both factory and aftermarket varieties, and in many configurations and even kits. Glow in the dark inserts are almost exclusively Tritium-doped polymer paints, or for high-end implementations, small Tritium vials held in specially designed high-impact brackets. See: Open sight

Nipple: A small metal tube extending through the breech of a percussion firearm through which the flame passes from the percussion cap to fire the powder charge.

Nose: The point of a projectile. Used in terms like "round nose" or sometimes "ball nose". Also called a point, as in "soft point".


Obturation: The expansion of the cartridge case which seals the chamber preventing gases from escaping.

Open bolt: An action design that, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine into the chamber and firing it. Most open bolt guns are or are derived from machine guns, and while having the advantage in terms of heat dissipation, are more prone to runaway firing, malfunction, and fouling than closed bolt designs.

Open Sight: A non-telescopic firearm sight. Most often refers to a traditional "notch and post" sight.

Optical Sight: Usually a telescopic firearm sight (often called a "scope"), but also refers to more modern red dot, holographic, or combination optics.

Over-And-Under Gun: A firearm, almost exclusively a shotgun, with two or more barrels placed one over the other. Contrast with: Side-by-side


Parallax: The displacement of an object viewed from two different position. For example, when using a telescopic sight, the apparent movement of the reticule in relation to the target when the eye is shifted to a different position.

Parkerizing: A non-reflecting, rust-preventive finish used on the metal of firearms. More effective at rust prevention than bluing, it is an electrochemical phosphate conversion. The Parkerizing process cannot be used on non-ferrous metals such as aluminum, brass, or copper. It similarly cannot be applied to steels containing a large amount of nickel, or on stainless steel.

Patch: A piece of leather or cloth. The patch is greased and placed around a bullet before ramming it down the barrel of a muzzleloader.

Patch Box: Covered compartment in the buttstock of a muzzle-loading rifle used to carry patches or other small items.

Pattern: Distribution of shotgun pellets. This is measured at a standard distance of 40 yards (37 m) using a 30 inch circle (762 mm). For example, a full choke charge should throw a pattern of at least 70 percent of the shot into the 30 inch circle at a distance of 40 yards.

Peep sight: A type of sight that uses a peephole as the rear aperture, and a post as the front sight. Most commonly seen on military rifles. See: Sight, Closed Sight

Penetration: The distance traveled by a projectile from the point where it strikes the target to the point where it stops. The United States FBI guidelines for effective stopping power indicate that a bullet at its maximum effective range should penetrate no less than 12 inches of ballistic gelatin.

Penetrator: A hardened steel core in certain kinds of bullet; Designed to penetrate armor or other materials that may stop the lead or jacketed lead projectile which contains it.

Percussion Cap: A small metal explosive-filled cup which is placed over the nipple of a percussion firearm. As the cap is struck by the hammer, it explodes and sends a flame through the flashhole in the nipple to the main powder charge.

Picatinny Rail: Informal name used to refer to any accessory mounting rail that conforms to, or is compatible with, MIL-STD-1913; sometimes called "13 rails".

Pistol Grip: See: Grip.

Pitch: The angle of the barrel of a rifle or shotgun away from the angle of the stock. (It is measured by placing the butt of the stock on the floor and measuring the angle of the muzzle away from a line perpendicular to the floor.)

Plus, Plus-P: See: +P, Magnum

Powder: The general term for any propellant used in firearms which burns upon ignition. The two major types are black powder, which is a physical mixture of charcoal, sulfur and saltpeter, and smokeless powder, any number of chemical formulations designed specifically for modern small arm. Note: Smokeless powder and black powder should NEVER be substituted for each other!

Prime: To prepare or charge a muzzle loader for firing.

Primer: The collective term for the chemical primer compound, cup and anvil which, when struck, ignites the powder charge.

Primer Cup: The housing in a shotgun cartridge base which holds a primer.

Primer Pocket: The depression in the base of a centerfire cartridge which contains the primer. See: Berdan Primer, Boxer Primer

Projectile: A bullet or shot in flight after discharge from a firearm.

Propellant: The chemical substance which imparts movement to the projectile in a firearm. See: Powder

Pump Action: A manual action by which the moving parts are actuated via a manually operated slide or "pump"; commonly seen on shotguns, and to a lesser extent rifles.

Pumpkin Ball: A large round ball of lead used in shotguns. These projectiles are the same size as the shotgun bore. Superseded mostly by slugs.



Rail: Can refer either to a Picatinny Rail or similar accessory-mounting fixture, or to any bearing surface or lug meant to allow only a single axis of movement, such as the slide rail of a pistol on which the slide moves forwards and backwards, or the upper and lower rails of a Kalashnikov-type action between which the bolt carrier rides.

Ramrod: A wood or metal rod used to force the wad and bullet down the barrel of a muzzle-loading firearm.

Range: The distance traveled by a projectile from the firearm to the target. Point-blank range is the distance a projectile will travel before it drops the extent that sight adjustment is required. Effective range is the greatest distance a projectile will travel with accuracy. Extreme range is the maximum distance a projectile will travel. Also, a facility designed for the safe shooting of firearms.

Receiver: Sometimes called a "frame" in pistols; The metal frame of a pistol, rifle or shotgun which contains the breech, locking mechanism and reloading mechanism. Also, in terms of US law, the part of the weapon which is legally considered to be the weapon, distinct from the other parts.

Receiver Ring: The portion of a receiver which is threaded so the barrel can be attached to it.

Receiver Sight: A sight attached to the receiver.

Recoil: The backward force of a firearm caused by expansion of powder gases which also impels the bullet out of the barrel. Recoil is measured in foot pounds. See: Kick.

Red Dot: A type of optical sight that projects a red dot onto a glass or polycarbonate window for use as a reticle. The red dot is the point of aim. May be used alone or in conjunction with magnifying optics. Care must be taken to establish the parallax of the red dot sight in question.

Reticule: The pattern of lines or dots that denote point of aim and other information in an optical sight. Many patterns exist.

Rifle: A shoulder firearm with a rifled barrel designed to fire one projectile at a time. See: Rifling.

Rifled Slug: A large, single projectile used in shotguns.

Rifling: Spiral grooves cut into the inside barrel surface to cause a bullet to spin, thereby stabilizing it. The cut-away portions of the rifling are called Grooves and the uncut portions are called Lands. See: Lands and Grooves.

Rim: The edge on the base of a cartridge case which stops the progress of the case into the chamber. It's also the part of the case the extractor grips to remove it from the chamber.

Rimfire: A cartridge in which the priming compound is contained in the rim at the base of the cartridge. See also: Cartridge.


SAAMI: The Sporting Arms and Ammunition Manufacturers' Institute; an association of American manufacturers of firearms, ammunition and components. Founded in 1926 at the request of the federal government and tasked with creating and publishing industry standards for safety, interchangeability, reliability and quality. Modern firearms are chambered to SAAMI specifications for a particular round, and are designed to operate within the tolerances provided by SAAMI specification ammunition.

Sabot: A sleeve used to hold and position a projectile that is smaller than the bore; most often seen explicitly referenced in regards to saboted slugs for use in rifled shotgun barrels.

Safety: A device that blocks the firing mechanism of a firearm. There are several types of safety, which may be grouped into two broad categories - manual, and passive. Manual safeties include those which must be operated by the shooter, such as a thumb safety or safety lever; and passive safeties, which are those which are integral to the function of the firearm, such as a grip safety or firing pin safety.

Sear: The part of a firearm which links the trigger and the firing pin and releases it when the trigger is pulled.

Sectional Density: The relationship between the weight of the bullet and the cross-sectional area.

Select-fire: A type of weapon that allows for semiautomatic and some combination of burst and/or automatic fire. Commonly seen on modern military weapons, e.g. the Colt M4A1 Carbine which is capable of semiautomatic or three round burst, or certain variants of the Heckler & Koch MP5 which are capable of semi, 3 or sometimes 5 round burst, and automatic fire.

Semi-Automatic: An action which fires, extracts, ejects, reloads and cocks with each separate pull of the trigger and is powered by the propellant gases. Also called autoloading, or in the case of pistols, automatic.

Setscrew: A screw that regulates the amount of pressure needed to release the sear.

Sewer pipe: Slang term for an exceptionally worn barrel, one in which the rifling is worn down so as to be imperceptible, and the metal permanently darkened from wear.

Shell: See: Cartridge.

Shot: Pellets of various sizes designed to be fired from a shotgun. Shot loads for various handgun calibers are widely available and are intended for use against small varmints or snakes. Usually formed in a shot tower.

Shot cup: The plastic or paper cup that holds the shot charge in a shotshell. Sometimes incorrectly referred to as a sabot.

Shotgun: A firearm with a smooth bore designed to fire small pellets called shot or rifled slugs.

Shotshell: See: Cartridge.

Shoulder: The sharply sloping portion of the cartridge case joining the body and neck. Found only on bottleneck shaped cartridge cases.

Side-by-side: A firearm, almost always a shotgun, with two barrels in a horizontal configuration. The traditional "double barreled shotgun".

Sight: The device on a firearm designed to help the shooter aim accurately. See: Closed Sight, Iron Sight, Open Sight, Optical Sight, Peep Sight

Slack: The amount of movement in a trigger mechanism before it engages the sear.

Sling: A strap used to carry and aid in shooting a rifle.

Sling Swivel: A metal loop, sometimes detachable, by which the sling is attached to the firearm. Sometimes also used to attach "universal" bipods.

Slug: Typically refers to a type of shotshell that is loaded with a single, large projectile with the same diameter as the bore, though sometimes used as a generic term for any type of solid, single-metal bullet, particularly of a large caliber.

Small Bore: Generally refers to a .22 caliber firearm.

Small-Of-The-Stock: The narrow portion of the stock between the comb and the receiver of a shoulder firearm.

Smokeless Powder: See: Powder.

Smooth Bore: A firearm with a bore that is not rifled, almost always a muzzleloader.

Snap Shot: A quick shot taken without deliberate aim.

Spent Bullet: A projectile which has lost nearly all its energy and lacks the force needed to penetrate the target. A bullet that is beyond its effective range.

Spitzer: A bullet with a sharp point for better stability during flight.

STANAG: Shorthand for "Standard NATO Agreement", most often used when referring to the type of magazine and ammunition that a particular weapon uses; most commonly "AR-type" magazines and 5.56 NATO.

Stock: The part of a shoulder firearm by which it is held for firing and into which the metal parts are fitted.

Straight-Pull Action: A bolt action in which the bolt is pulled and pushed straight backward and forward.

Striker: The front part of a firing pin which strikes the cartridge.

Stripper clip: See: Clip

Swivel: See: Sling Swivel.


Tang: A metal strip extending rearward from a rifle or shotgun receiver to attach the action to the stock; also the protruding upper portion of a pistol grip.

Three dot: See: 3-dot

Throat: The forward portion of the chamber where it is tapered to meet the bore.

Toe: The bottom part of the butt of a rifle or shotgun.

Trajectory: The path a bullet travels from muzzle to impact.

Trigger: The part of a firearm mechanism which releases the firing pin.

Trigger Guard: A metal loop around the trigger designed to protect it.

Trigger Plate: The metal part under the receiver of a rifle or shotgun through which the trigger projects.

Trombone Action: A pump or slide action. See: Pump action

Turn-Bolt Action: A bolt action which is locked by pressing the bolt handle in and down, thereby turning its locking lugs into the receiver.

Twist: The angle of rifling grooves relative to the bore axis. (Expressed as the distance in inches over which a turn or twist is completed, i.e., 1/10, 1/22.)



Velocity: The speed at which a projectile travels. Usually measured in feet per second or meters per second, and most commonly used to discuss muzzle velocity and impact velocity.


Wad: A disc used to separate powder from shot; or to seal propellant gases behind the shot; or to hold shot together in the barrel.

Wadcutter: A special-purpose bullet specially designed for shooting paper targets, usually at close range and at subsonic velocities. It is easily identified by the flat nose, intended to punch very clean holes in paper. They will very quickly foul a barrel when fired at higher velocities, which can be a danger when following up with jacketed rounds.

Wildcat Cartridge: A non-standard cartridge usually made by modifying the shape of a standard cartridge, or be deliberately exceeding the minimum or maximum specifications of one or more load parameters.

Windage: The lateral drift of a bullet in flight caused by wind. Also used to refer to adjustments made to a firearm's sights to correct the point of impact for left-right distance.

Wizard: A term used to refer to a very badly misaligned scope or optic. Ideally, when zeroed, a scope should be near to the center of its x- and y-axis adjustment, but a "wizard scope" or "wizardy scope" will be very far to one end of one or both of the adjustments when zeroed in order to compensate for scope mounts that are poorly aligned with the bore.




Zero: Sight adjustment so the bullet will strike the target at the point of aim at the distance specified.

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