all things correct including purchasing them with out an fflYou could print a pistol frame or AR lower with current 3D printer technology. You'll always need metal for the barrel/breech/firing pin. But polymer pistol frames are already a thing, and with that being the serial numbered part on most pistols, like the lower is for an AR, it opens the door to people getting around FFL limitations to obtaining firearms. Not that there isn't already a black market dedicated to exactly that, but you get my point.