It is generally unlawful to import a machine gun into the United States for unrestricted sale. However, machine guns that are properly destroyed to ATF specifications may be imported.
A machine-gun parts kit is generally importable so long as the kit does not include a machine gun, barrel, frame or receiver. Note that machine gun destruction to ATF specifications will generally render a machine-gun parts kit importable in this respect (destroying a kit’s barrel, and/or frame, and/or receiver to ATF specifications so they are no longer considered a barrel, frame or receiver will generally render the kit importable in this respect).
Importations are subject to country restrictions. For example, machine-gun parts kits from firearms manufactured in Russia or one of the former Soviet States are not importable. Machinegun parts kits (excluding the frame, receiver or barrel) from a surplus military U.S.-origin machine gun will also require retransfer authorization from the U.S. Department of State.
[18 U.S.C. § 922(o); 26 U.S.C. § 5844; 22 U.S.C. § 2778; 27 CFR § 447.11, 447.21, 447.41, 447.52]