Making or assembling is just that. The part that people stumble upon is the letter regarding shortening the barrel of an AK variant. Many keyboard kommandos interpreted that to mean that making an SBR/NFA weapon exempted you from 922(r). What was left out was the question that was asked to generate the response. The question that was asked was along the lines of "if all I am doing is shortening the barrel of an otherwise lawfully imported weapon, does 922(r) apply?" ATF held that just shortening the barrel does not constitute an act of making or assembly. Changing out components absolutely would, though. Just shorten the barrel, no problem. Swap out the butt stock, problem.

And to say it again... there is no possession offense listed in 922(r). If you bought it that way, you did not make or assemble it.