when I was reading up on his adventures, basically an ATF agent could in 80 minutes (eighty) to make gun fireable and hence they claim "readily convertible to a firearm, i.e. it's a gun" ...
#1, 80 minutes for an expert with all the right tools and equipment is a hell of a time. Shit, you can do a lot in 80 minutes.
#2, making a 50 BMG readily to fire and AK ready to fire are two different things. A ****ed 50BMG rifle could blow up with catastrophic results, a chance no sane man would take, so technically it would take more than 80 minutes to make his "receiver" ready.
That's basically it. ATF ****ed him. Case closed. I can see Ares treading more carefully while poking ATF's vagina.