Being completely unconstitutional anyways, when the NFA/GCA/FOPA lets a shoestring be a machine gun, a 1/4" hole in an AR15 receiver (the empty hole of air) declared a machine gun, and the inconsistencies and backtracking of the NFA Technologies branch (Atkins bump-fire machine gun "springs"), then the law needs to be scrapped.
No law should be so onerous and confusing to trap innocent law-abiding citizens. There are people in prison for paperwork errors and their business and livelihood destroyed by ATF technical bureaucratic edicts......that is if they don't murder you first.