<Dl> <Dd> The term "firearm" means a shotgun or rifle having a barrel of less than eighteen inches in length, or any other weapon, except a pistol or revolver, from which a shot is discharged by an explosive if such weapon is capable of being concealed on the person, or a machine gun, and includes a muffler or silencer for any firearm whether or not such firearm is included within the foregoing definition . </Dd> </Dl> <Dd> The term "firearm" means a shotgun or rifle having a barrel of less than eighteen inches in length, or any other weapon, except a pistol or revolver, from which a shot is discharged by an explosive if such weapon is capable of being concealed on the person, or a machine gun, and includes a muffler or silencer for any firearm whether or not such firearm is included within the foregoing definition . </Dd> <P> Under the original Act, NFA weapons were machine guns, short - barreled rifles (SBR), short - barreled shotguns (SBS), any other weapons (AOW or concealable weapons other than pistols or revolvers), and silencers for any type of NFA or non-NFA . Minimum barrel length was soon amended to 16 inches for rimfire rifles and by 1960 had been amended to 16 inches for centerfire rifles as well . </P> <P> The United States Supreme Court, in 1968 decided the case of Haynes v. United States in favor of the defendant, which effectively gutted the National Act of 1934 . As one could possess an NFA firearm and choose not to register it, and not face prosecution due to Fifth Amendment protections, the Act was unenforceable . To deal with this, Congress rewrote the Act to make registration of existing weapons impossible except by the government (previously, an existing firearm could be registered by any citizen). In addition to fixing the defect identified in Haynes, the revision tightened definitions of the firearms regulated by the Act, as well as incorporating a new category of firearm, the Destructive Device, which was first regulated in the Omnibus Crime Control and Safe Streets Act of 1968 . </P>

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