They are just using this to try and regulate and suppress a perfectly legal activity. An citizenry armed with weapons that they don't know about scares the hell out of them.
>>This is highly misleading. Anyone can already buy a stripped lower receiver without going through a FFL and assembling an AR.
Simply not true. The stripped lower receiver of an AR *is* “the gun” legally, and buying one requires BATFE paperwork and background check.
This brings up the whole issue of “what part makes the gun?” With an FAL, for instance, it is the upper receiver that is the serial numbered part that “counts”, and not the lower. I never did understand why the lower was the part on ARs, but that is the deal.
I’m pretty sure that a stripped lower is still considered a firearm by the ATF. To avoid being considered a firearm, it needs to be less than 80% complete, i.e. a significant amount of skilled machining is required.
Upper receivers are not controlled.