A parts kit is a collection of weapon (notably

firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...

) parts that, according to the

Bureau of Alcohol, Tobacco, Firearms, and Explosives The Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), commonly referred to as the ATF, is a domestic law enforcement agency within the United States Department of Justice. Its responsibilities include the investigation and preven ...

(ATF), "is designed to or may be readily be assembled, completed, converted, or restored to expel a projectile by the action of an explosive." As an example, the kit may not include a receiver or include an incomplete receiver. In most cases under

U.S. law The law of the United States comprises many levels of Codification (law), codified and uncodified forms of law, of which the most important is the nation's Constitution of the United States, Constitution, which prescribes the foundation of the ...

, the receiver must be serialized, and it requires a background check to purchase, among other considerations. This is different from other countries where pressure bearing parts such as bolts,

barrels A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, u ...

, and gas pistons are the regulated parts. A receiver can be purchased or manufactured to complete the firearm. The

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 ...

(NFA) restricts the possession of automatic firearms, so most parts kits end up used with a semi-automatic receiver. In addition, under US gun law, a receiver that is legally a

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 rifles) a ...

cannot legally become semi-automatic. There is no federal restriction on the purchase and import of machine gun parts kits (minus the barrel), however. Parts kits are available for many firearms including 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 Corporation d ...

and

AKM The AKM () is an assault rifle designed by Soviet small arms designer Mikhail Kalashnikov in 1959. It is the most ubiquitous rifle of the Kalashnikov rifles. It was developed as a replacement to the AK-47 introduced a decade prior. Introduced ...

variants.

References

Firearm components {{firearms-stub