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 A gunsmith is a person who repairs, modifies, designs, or builds guns. The occupation differs from an armorer, who usually replaces only worn parts in standard firearms. Gunsmiths do modifications and changes to a firearm that may require a very ...

Modifications performed

Common modifications include: * Cosmetic and ergonomic modifications ** Replacement or alteration of grips or stocks ** Changing of sights, such as the adjustable

iron sights Iron sights are a system of physical alignment markers (usually made of metallic material) used as a sighting device to assist the accurate aiming of ranged weapons (such as a firearm, airgun, crossbow or even compound bow), or less commonl ...

or a

telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a '' reticle'' – mounted in a focally appropriate ...

** Adding or removing weight to ease carrying, alter balance, or help moderate

recoil Recoil (often called knockback, kickback or simply kick) is the rearward thrust generated when a gun is being discharged. In technical terms, the recoil is a result of conservation of momentum, as according to Newton's third law the force r ...

** Metal engraving or custom woodwork ** Checkering or stippling wood or metal ** Altering the metal finish, using techniques such as bluing,

electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...

, or

parkerizing Phosphate conversion coating is a chemical treatment applied to steel parts that creates a thin adhering layer of iron, zinc, or manganese phosphates, to achieve corrosion resistance, lubrication, or as a foundation for subsequent coatings o ...

** Use of a shorter barrel to reduce size and weight, or a longer barrel to increase velocity * Caliber conversions ** Rechambering or rebarreling for a new caliber, such as conversions made to chamber a

wildcat cartridge A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic (such as the power, ...

** Use of a

caliber conversion sleeve A caliber conversion sleeve or adapter sleeve is a device which can be used to non-permanently alter a firearm to allow it to fire a different cartridge than the one it was originally designed to fire. The different cartridge must be smaller in ...

or other readily removable insert to fire a smaller, less expensive cartridge * Operating mechanism conversions **

Muzzleloading Muzzleloading is the shooting sport of firing muzzleloading guns. Muzzleloading guns, both antique and reproduction, are used for target shooting, hunting, historical re-enactment and historical research. The sport originated in the United States ...

paper cartridge A paper cartridge is one of various types of small arms ammunition used before the advent of the metallic cartridge. These cartridges consisted of a paper cylinder or cone containing the bullet, gunpowder, and in some cases, a primer or a lub ...

to metallic cartridge conversions, such as the Allin conversion or Lund conversion ** Conversion from

fully automatic An automatic firearm is an auto-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 disch ...

select fire Selective fire is the capability of a weapon to be adjusted to fire in semi-automatic, fully automatic, and/or burst mode. The modes are chosen by means of a selector switch, which varies depending on the weapon's design. Some selective-fire w ...

to semiautomatic only or manual operation, or vice versa ** Short recoil to blowback conversions, used in various

.22 Long Rifle The .22 Long Rifle or simply .22 LR or 22 (metric designation: 5.6×15mmR) is a long-established variety of .22 caliber rimfire ammunition originating from the United States. It is used in a wide range of rifles, pistols, revolvers, smo ...

conversions, such as the Colt Ace and J. A. Ceiner conversion kits. ** Conversion from

handgun A handgun is a short- barrelled gun, typically a firearm, that is designed to be usable with only one hand. It is distinguished from a long gun (i.e. rifle, shotgun or machine gun, etc.), which needs to be held by both hands and also brac ...

carbine A carbine ( or ) is a long gun that has a barrel shortened from its original length. Most modern carbines are rifles that are compact versions of a longer rifle or are rifles chambered for less powerful cartridges. The smaller size and light ...

or rifle ** Addition of a rifled barrel to a

shotgun A shotgun (also known as a scattergun, or historically as a fowling piece) is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which usually discharges numerous small pellet-like spherical sub- p ...

to allow it to better fire

shotgun slug A shotgun slug is a heavy projectile made of lead, copper, or other material and fired from a shotgun. Slugs are designed for hunting large game, and other uses, particularly in areas near human population where their short range and slow speed h ...

s *

Accurizing Accurizing is the process of improving the accuracy and precision of a gun ( firearm or airgun). For firearms, accuracy is the ability to hit exactly what one is aiming at, and precision is the ability to hit the same place over and over again ...

* Sporterizing Some commonly customized firearms include the

Ruger 10/22 The Ruger 10/22 is a series of semi-automatic rifles produced by American firearm manufacturer Sturm, Ruger & Co., chambered for the .22 Long Rifle rimfire cartridge. It uses a patented 10-round rotary magazine, though higher capacity box ma ...

carbine, the

M1911 pistol The M1911 (Colt 1911 or Colt Government) is a single-action, recoil-operated, semi-automatic pistol chambered for the .45 ACP cartridge. The pistol's formal U.S. military designation as of 1940 was ''Automatic Pistol, Caliber .45, M1911'' for t ...

, and the

AR-15 An AR-15-style rifle is any lightweight semi-automatic rifle based on the Colt AR-15 design. The original ArmaLite AR-15 is a scaled-down derivative of Eugene Stoner's ArmaLite AR-10 design. The then Fairchild Engine and Airplane Corporat ...

rifle, all of which have large numbers of aftermarket parts suppliers. Shooting disciplines such as bullseye pistol and

benchrest shooting Benchrest shooting is a shooting sport discipline in which high-precision rifles are rested on a table or bench — rather than being carried in the shooter's hands — while shooting at paper or steel targets, hence the name "benchrest". Bot ...

also rely extensively on custom-built and modified firearms to achieve top accuracy.

Legal issues

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 The National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, was enacted on June 26, 1934, and currently codified and amended as . The law is an Act of Congress in the United States that, in general, imposes an excise tax on the manufact ...

, which define restricted classes of firearms. Examples of illegal firearms under this act are: *Rifles with overall lengths under 26 inches, or barrels under 16 inches in length *Shotguns with overall lengths under 26 inches, or barrels under 18 inches in length *

Machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifl ...

s *A conversion to a fixed cartridge of over .50 caliber These restrictions vary from location to location; some areas may restrict magazine capacity or require special safety devices such as

loaded chamber indicator Close-up shot of a safety of an M16A2 rifle In firearms, a safety or safety catch is a mechanism used to help prevent the accidental discharge of a firearm, helping to ensure safer handling. Safeties can generally be divided into subtypes suc ...

s, integral locking mechanisms, magazine disconnects. Also commonly required are identifying marks such as serial numbers or firearm microstamping components, removal of which may be illegalSee Gun Control Act of 1968 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 The Firearm Owners' Protection Act (FOPA) of 1986 is a United States federal law that revised many provisions of the Gun Control Act of 1968. Federal firearms law reform Under the Gun Control Act of 1968, the Bureau of Alcohol, Tobacco, Firea ...

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."

References

Firearm terminology

Modifications performed

Legal issues

See also

References