A 2004 ATF letter re: rewelds of machine gun receivers

Summary of Letter

• Forward grip on Hungarian AMD-63 and AMD-65 rifles, for 922(r) purposes, is considered to be a part of the forearm.
• When designing semi-auto receiver for these rifles, receiver may not accept original components, and weapon must fire from closed bolt.
• Replacement receivers may be newly manufactured or built from demilled receiver pieces. Proper demil requires diagonal torch cuts in three critical locations, displacing at least 1/4" of material.
• If re-using receiver parts, the third hole and slotted right receiver rail must be removed.
• No need to serialize self-built weapons unless they're being transferred.
• C&R FFL does not authorize its holder to manufacture weapons for commercial resale.

Actual Letter