Federal law, to the degree that I understand it, is that anyone who has no background prohibitions can build a firearm of his/her own as long as he doesn't sell it, it's the selling that draws the legal problems. So if some kind hearted person makes a firearm and gives it to his kid (Of age) or a friend he knows there's no problem. Of course in states like mine where tyrants rule the Bill of Rights doesn't apply (Boggles my mind typing that) and I'd have to have a background check done to even give a gun I made to a friend I've known for 50 years, of course it doesn't make any sense, nor do tyrants need it to, the object is to restrict gun ownership and use, you know, the "Keep and bear" stuff.
But the guy running the "Build your own AR" parties, did he get paid for the machine usage, or the knowledge of what to do?
I don't understand why the BATF cannot consider two component parts of a single gun to both be the firearm, after all, any single baffle of a suppressor is considered a suppressor for legal means, how is that different?