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 gun (MG) is a fully automatic and rifled firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles are typically designed more for firing short bursts rather than continuous firepower and are not considered true machine guns. Submachine guns fire handgun cartridges rather than rifle cartridges, therefore they are not considered machine guns, while automatic firearms of 20 mm (0.79 in) caliber or more are classified as autocannons rather than machine guns.
A revolver is a repeating handgun with at least one barrel and a revolving cylinder containing multiple chambers for firing. Because most revolver models hold up to six cartridges, before needing to be reloaded, revolvers are commonly called six shooters or sixguns. Due to their rotating cylinder mechanism, they may also be called wheel guns.
The National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, 48 Stat. 1236 was enacted on June 26, 1934, and currently codified and amended as I.R.C. ch. 53. The law is an Act of Congress in the United States that, in general, imposes an excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The NFA is also referred to as Title II of the federal firearms laws, with the Gun Control Act of 1968 ("GCA") as Title I.
In firearms terminology and law, the firearm frame or receiver is the part of a firearm which integrates other components by providing housing for internal action components such as the hammer, bolt or breechblock, firing pin and extractor, and has threaded interfaces for externally attaching ("receiving") components such as the barrel, stock, trigger mechanism and iron/optical sights. Some firearm designs, such as the AR-15 platform, feature receivers that have 2 separate sub-assemblies called the upper receiver which houses the barrel/trunnion, bolt components etc and the lower receiver that holds the fire control group, pistol grip, selector, stock etc.
A repeating rifle is a single-barreled rifle capable of repeated discharges between each ammunition reload. This is typically achieved by having multiple cartridges stored in a magazine and then fed individually into the chamber by a reciprocating bolt, via either a manual or automatic action mechanism, while the act of chambering the round typically also recocks the hammer/striker for the following shot. In common usage, the term "repeating rifle" most often refers specifically to manual repeating rifles, as opposed to self-loading rifles, which use the recoil, gas, or blowback of the previous shot to cycle the action and load the next round, even though all self-loading firearms are technically a subcategory of repeating firearms.
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 hell-fire trigger is a device that allows a semi-automatic firearm to fire at an increased rate. The hell-fire clamps to the trigger guard behind the trigger and presses a "finger" against the back of the trigger to increase the force that returns the trigger to its forward position, effectively decreasing the time required for the trigger to reset, allowing for a faster follow-up shot.
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 trigger is a mechanism that actuates the function of a ranged weapon such as a firearm, airgun, crossbow, or speargun. The word may also be used to describe a switch that initiates the operation of other non-shooting devices such as a trap, a power tool, or a quick release. A small amount of energy applied to the trigger leads to the release of much more energy.
Bump stocks or bump fire stocks are gun stocks that can be used to assist in bump firing, the act of using the recoil of a semi-automatic firearm to fire cartridges in rapid succession.
Dry firing is the act of activating the firing mechanism a bow, crossbow, firearm or other projectile discharging weapon while unloaded or without live ammunition. The expression is also used to refer to practicing with an inert laser/infrared training platform and may also include the use of a target/feedback system.
Title II weapons, or NFA firearms, are designations of certain weapons under the United States National Firearms Act (NFA).
The Sputter Gun was a prototype test gun using 7 major components from the WW2 era British Sten submachine gun carbine, along with other specially fabricated parts to make a complete operational firearm. It was designed to circumvent the existing U.S. Federal law defining a machine gun. The Sputter Gun, lacking any trigger, was designed to fire multiple rounds automatically, upon release of the bolt from its safety slot, until all ammunition was expended from the magazine.
A homemade firearm, also called a ghost gun or privately made firearm, is a firearm made by a private individual, in contrast to one produced by a corporate or government entity. The term ghost gun is used mostly in the United States by gun control advocates, but it is being adopted by gun rights advocates and the firearm industry.
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.
A Glock switch is a small device that can be attached to the rear of the slide of a Glock handgun, changing the semi-automatic pistol into a selective fire machine pistol capable of fully automatic fire. As a type of auto sear, it functions by applying force to the trigger bar to prevent it from limiting fire to one round of ammunition per trigger pull. This device by itself, regardless if it is installed on a slide or not, is classified by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to be a machine gun, making possession of the device illegal in the United States under most circumstances.
Garland v. Cargill, 602 U.S. 406 (2024), was a United States Supreme Court case regarding the classification of bump stocks as "machine guns" under the National Firearms Act of 1934 (NFA) by the United States Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) in 2018. In a 6–3 decision, the Supreme Court ruled that bump stocks are not machine guns for purposes of the NFA, vacating the ATF rule and finding that the ATF exceeded its statutory authority.
A binary trigger is a type of device that allows a semi-automatic firearm to fire at an increased rate. A binary trigger works by firing one shot upon pulling the trigger and then firing a subsequent shot upon release of the trigger.
A trigger crank is a device that allows a semi-automatic firearm to fire at an increased rate. The trigger crank typically consists of a screw-tight clamp and crank assembly. The crank assembly is clamped onto the trigger guard of a semi-automatic firearm. The device is positioned in front of the trigger. When the crank is turned, tiny gears depress the trigger and cause the weapon to fire.
