BTW, the whole "80%" thing is a nonsense term, just like "assault weapon" that we made up to describe a product the ATF has ruled "not a firearm." Same as they would rule a soup can. That ruling was based on a certain amount of time, difficulty, and expense, and if a turn key CNC setup* comes along to greatly ease the process, the ATF will rule more restrictively. 20% or whatever percentage has nothing to do with it; it's at their discretion that the unfinished lowers are available without FFL
Since the ATF gets to 'write' their enforcement determinations, we have little to gain and much to lose if we do stuff to push the boundaries and blur their definitions. This isn't like law where precedent rules the day; any new director can order or be ordered to change their opinions. Rarely towards less restriction, or course (but sometimes)
*people always forget the enormous amount of prep work involved, which for something simple like finishing a lower, is really a waste of money and machine time since a manual mill is just about as fast, and much easier for a newb to run than a CNC (yes, you still have to run them)
"I don't believe that the men of the distant past were any wiser than we are today. But it does seem that their science and technology were able to accomplish much grander things."
-- Alex Rosewater