The 1994 Federal Assault Weapons Ban, which expired on September 13, 2004, codified the definition of an assault weapon. It defined the rifle type of assault weapon as a semiautomatic firearm with the ability to accept a detachable magazine and two or more of the following:
a folding or telescoping stock
a pistol grip that protrudes conspicuously beneath the action of the weapon
a bayonet mount
a flash suppressor or threaded barrel designed to accommodate a flash suppressor
a grenade launcher