Firearm modification is commonly done in order to enhance various aspects of the performance of a firearm. Reasons for these modifications can range from cosmetic to functional, and can be simple operations that the owner can perform, or complex operations requiring the services of a gunsmith.
Common modifications include:
Some commonly customized firearms include the Ruger 10/22 carbine, the M1911 pistol, and the AR-15 rifle, all of which have large numbers of aftermarket parts suppliers. Shooting disciplines such as bullseye pistol and benchrest shooting also rely extensively on custom-built and modified firearms to achieve top accuracy.
Care must be taken when modifying firearms, as some operations may convert a legal firearm into an illegal one. An example of this is the restrictions in the US National Firearms Act, which define restricted classes of firearms. Examples of illegal firearms under this act are:
These restrictions vary from location to location; some areas may restrict magazine capacity or require special safety devices such as loaded chamber indicators, integral locking mechanisms, magazine disconnects. Also commonly required are identifying marks such as serial numbers or firearm microstamping components, removal of which may be illegal [4] [5] [6] Furthermore - conversion of semi-automatic weapons into select-fire weapons has been illegal for non-SOT holding gunsmiths since the passage of the Hughes Amendment in 1986. Such weapons may be held only by law enforcement and military only except for "dealer samples" left in the hands of SOT holders. Fully automatic weapons converted to semi-automatic only operation are machine guns per the NFA. The BATFE's policy is "Once a machine gun, always a machine gun."
A carbine, from French carabine, is a long gun firearm but with a shorter barrel than a rifle or musket. Many carbines are shortened versions of full-length rifles, shooting the same ammunition, while others fire lower-powered ammunition, including types designed for pistols.
A firearm is a portable gun designed for use by a single individual. It inflicts damage on targets by launching one or more projectiles driven by rapidly expanding high-pressure gas produced by exothermic combustion (deflagration) of chemical propellant within an ammunition cartridge. If gas pressurization is achieved through mechanical gas compression rather than through chemical propellant combustion, then the gun is technically an air gun, not a firearm.
Single-shot firearms are firearms that hold only a single round of ammunition, and must be reloaded after each shot. The history of firearms began with single-shot designs, and many centuries passed before multi-shot repeater designs became commonplace. Single-shot designs are less complex than revolvers or magazine-fed firearms, and many single-shot designs are still produced by many manufacturers, in both cartridge- and non-cartridge varieties, from zip guns to the highest-quality shooting-match weapons.
A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwanted muzzle rise. The concept was first introduced for artillery and was a common feature on many anti-tank guns, especially those mounted on tanks, in order to reduce the area needed to take up the strokes of recoil and kickback. They have been used in various forms for rifles and pistols to help control recoil and the rising of the barrel that normally occurs after firing. They are used on pistols for practical pistol competitions, and are usually called compensators in this context.
In firearms terminology, an action is the mechanism of a breech-loading weapon that handles the ammunition or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all are single-shot weapons with a closed off breech. Instead, the ignition mechanism is referred to: matchlock, flintlock, etc.
The National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, 48 Stat. 1236, enacted on June 26, 1934, currently codified as amended as I.R.C. ch. 53, is an Act of Congress in the United States that, in general, imposes a statutory excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The Act was passed shortly after the repeal of Prohibition. The NFA is also referred to as Title II of the Federal firearms laws. The Gun Control Act of 1968 ("GCA") is Title I.
A semi-automatic firearm, also called self-loading firearm or autoloading firearm, is one that not only fires a bullet each time the trigger is pulled, but also performs all steps necessary to prepare it to discharge again—assuming cartridges remain in the firearm's feed device. Typically, this includes extracting and ejecting the spent cartridge case from the firing chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber. To fire again, the trigger is released and re-pressed.
A sawn-off shotgun also called a sawn-off shotgun and a short-barreled shotgun, is a type of shotgun with a shorter gun barrel—typically under 18 inches—and often a shortened or absent stock. Despite the colloquial term, barrels do not, strictly speaking, have to be shortened with a saw. Barrels can be manufactured at shorter lengths as an alternative to traditional, longer barrels. This makes them easier to transport due to their smaller profile and lighter weight. The design also makes the weapon easy to maneuver in cramped spaces, a feature sought by military close quarters combat units, law enforcement SWAT team users, and home defense purposes. As a result of the shorter barrel length, any sawed-off shotgun with a magazine tube will have its capacity reduced.
The Saiga-12 is a 12-gauge shotgun available in a wide range of configurations, patterned after the Kalashnikov series of rifles and named for the Saiga antelope. Like the Kalashnikov rifle variants, it is a rotating bolt, gas-operated gun that feeds from a box 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.
The ArmaLite AR-7 Explorer is a semi-automatic firearm in .22 Long Rifle caliber, developed in 1959 from the AR-5 that was adopted by the U.S. Air Force as a pilot and aircrew survival weapon. The AR-7 was adopted and modified by the Israeli Air Force as an aircrew survival weapon in the 1980s.
The Thompson/Center Contender is a break-action single-shot pistol or rifle that was introduced in 1967 by Thompson/Center Arms. It can be chambered in cartridges from .22 Long Rifle to .45-70 Government.
The Marlin Model 336 is a lever-action rifle and carbine made by Marlin Firearms. Since its introduction in 1948, it has been offered in a number of different calibers and barrel lengths, but is commonly chambered in .30-30 Winchester or .35 Remington, using a 20- or 24-inch barrel. Currently, the model with a 24-inch barrel is only available in .30-30 Winchester. The Model 336 is currently produced by Remington Arms.
A combination gun is a firearm that comprises at least one rifled barrel and one smoothbore barrel, that is typically used with shot or some types of shotgun slug. Most have been break-action guns, although there have been other designs as well. Combination guns using one rifled and one smoothbore barrel usually are in an over and under configuration. Side-by-side versions are referred to as cape guns. A drilling is a combination gun that has three barrels. A vierling has four barrels. Combination guns generally use rimmed cartridges, as rimless cartridges are more difficult to extract from a break-action weapon.
Short-barreled rifle (SBR) is a legal designation in the United States, referring to a shoulder-fired, rifled firearm, made from a rifle, with a barrel length of less than 16 in (41 cm) or overall length of less than 26 in (66 cm), or a handgun fitted with a buttstock and a barrel of less than 16 inches length. In the United States, an SBR is an item regulated by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) as a Title II weapon. In the absence of local laws prohibiting ownership, American civilians may own an SBR provided it is registered with the ATF, and a $200 tax is paid prior to taking possession of or creating the firearm.
The KRISS Vector series are a family of weapons based upon the parent submachine gun design developed by the American company KRISS USA, formerly Transformational Defense Industries (TDI). They use an unconventional delayed blowback system combined with in-line design to reduce perceived recoil and muzzle climb.
The following are terms related to firearms and ammunition topics.
Title II weapons, or NFA firearms, are designations of certain weapons under the United States National Firearms Act (NFA).