A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries.
A machine pistol is a handgun that is capable of fully automatic fire, including stockless handgun-style submachine guns.
A shotgun is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which discharges numerous small spherical projectiles called shot, or a single solid projectile called a slug. Shotguns are most commonly used as smoothbore firearms, meaning that their gun barrels have no rifling on the inner wall, but rifled barrels for shooting sabot slugs are also available.
A semi-automatic rifle is an auto-loading rifle that fires a single round of ammunition each time the trigger is pulled. It uses a part of the fired cartridge's energy to eject the case, and automatically loads another cartridge into its chamber. This is in contrast to bolt-action or lever-action rifles, which require the user to manually chamber a new round before they can fire again, and fully automatic rifles, which fire continuously when the trigger is held down.
In firearms terminology, an action is the functional mechanism of a breechloading firearm that handles the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock.
A semi-automatic firearm, also called a self-loading or autoloading firearm, is a repeating firearm whose action mechanism automatically loads a following round of cartridge into the chamber and prepares it for subsequent firing, but requires the shooter to manually actuate the trigger in order to discharge each shot. Typically, this involves the weapon's action utilizing the excess energy released during the preceding shot to unlock and move the bolt, extracting and ejecting the spent cartridge case from the chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber, all without input from the user. To fire again, however, the user must actively release the trigger, and allow it to "reset", before pulling the trigger again to fire off the next round. As a result, each trigger pull only discharges a single round from a semi-automatic weapon, as opposed to a fully automatic weapon, which will shoot continuously as long as the ammunition is replete and the trigger is kept depressed.
A semi-automatic pistol is a repeating handgun that automatically ejects and loads cartridges in its chamber after every shot fired, but only one round of ammunition is fired each time the trigger is pulled. The pistol's fire control group disconnects the trigger mechanism from the firing pin/striker until the trigger has been released and reset manually, unlike the self-cycled firing mechanism in fully automatic pistols.
An automatic firearm or fully automatic firearm is a self-loading firearm that continuously chambers and fires rounds when the trigger mechanism is actuated. The action of an automatic firearm is capable of harvesting the excess energy released from a previous discharge to feed a new ammunition round into the chamber, and then igniting the propellant and discharging the projectile by delivering a hammer or striker impact on the primer.
A magazine, often simply called a mag, is an ammunition storage and feeding device for a repeating firearm, either integral within the gun or externally attached. The magazine functions by holding several cartridges within itself and sequentially pushing each one into a position where it may be readily loaded into the barrel chamber by the firearm's moving action. The detachable magazine is sometimes colloquially referred to as a "clip", although this is technically inaccurate since a clip is actually an accessory device used to help load ammunition into a magazine or cylinder.
A firearm is said to fire from an open bolt or open breech if, when ready to fire, the bolt and working parts are held to the rear of the receiver, with no round in the chamber. When the trigger is actuated, the bolt travels forward, feeds a cartridge from the magazine or belt into the chamber, and fires that cartridge in the same movement. Like any other self-loading design, the action is cycled by the energy released from the propellant, which sends the bolt back to the rear, compressing the mainspring in readiness for firing the next round. In an open-bolt gun firing semi-automatically, the bolt is caught and held at this point by the sear after each shot; and in automatic open-bolt fire, it's caught and held in this manner whenever the trigger is released. In contrast to this, in closed-bolt guns, the trigger and sear do not affect the movement of the bolt directly.
A riot shotgun is a shotgun designed or modified for use as a primarily defensive weapon, by the use of a short barrel and sometimes a larger magazine capacity than shotguns marketed for hunting. The riot shotgun is used by military personnel for guard duty and was at one time used for riot control, and is commonly used as a door breaching and patrol weapon by law enforcement personnel, as well as a home defense weapon by civilians. Guns of this type are often labeled as breaching shotguns, tactical shotguns or special-purpose shotguns to denote the larger scope of their use; however, these are largely marketing terms.
The Saiga-12 is a shotgun available in a wide range of configurations, patterned after the Kalashnikov series of rifles and named after the Saiga antelope native to Russia. Like the Kalashnikov rifle variants, it is a rotating bolt, long-stroke gas piston operated firearm that feeds from a square magazine. All Saiga-12 configurations are recognizable as Kalashnikov-pattern guns by the large lever-safety on the right side of the receiver, the optic mounting rail on the left side of the receiver and the large top-mounted dust cover held in place by the rear of the recoil spring assembly. Saiga firearms are meant for civilian domestic sale in Russia, and export to international markets.
Rotating bolt is a method of locking the breech of a firearm closed for firing. Johann Nicolaus von Dreyse developed the first rotating bolt firearm, the "Dreyse needle gun", in 1836. The Dreyse locked using the bolt handle rather than lugs on the bolt head like the Mauser M 98 or M16. The first rotating bolt rifle with two lugs on the bolt head was the Lebel Model 1886 rifle. The concept has been implemented on most firearms chambered for high-powered cartridges since the 20th century.
The Heckler & Koch HK CAWS is a prototype automatic shotgun—designed as a combat shotgun—co-produced by Heckler & Koch and Winchester/Olin during the 1980s. It was Heckler & Koch's entry into the U.S. military's Close Assault Weapon System program.
The Volkssturmgewehr is the name of several rifle designs developed by Nazi Germany during the final months of World War II. They share the common characteristic of being greatly simplified as to adapt with the severe lack of resources and industrial capacity in Germany during the final stages of the war. The Volkspistole was a partner program, almost identical, but for pistols instead.
The KRISS Vector is a series of weapons based upon the parent submachine gun design developed by the American company KRISS USA, formerly Transformational Defense Industries (TDI).
The following are terms related to firearms and ammunition topics.
An automatic shotgun is an automatic firearm that fires shotgun shells and uses some of the energy of each shot to automatically cycle the action and load a new round. It will fire repeatedly until the trigger is released or ammunition runs out. Automatic shotguns have a very limited range, but provide tremendous firepower at close range.
Recoil operation is an operating mechanism used to implement locked-breech autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action, as opposed to gas operation or blowback operation using the pressure of the propellant gas.
A repeating firearm or repeater is any firearm that is designed for multiple, repeated firings before the gun has to be reloaded with new ammunition.
