An annoyance of mine when it comes to the firearms industry. Most everything is in writing, written at about the 9th grade level, and anyone can find it. Yet because some dealers were too hard headed to understand the simple instructions on the 4473, or like one of my old managers never read them, the ATF put it out twice that a receiver is just a receiver. Anyone can go the ATF website and view everything the ATF has published, from the FAQ to their publications of open and news letters. Not much is actually contradictory. Outside of the few well published cases, usually involving the Firearms Technical Branch, the regs and laws, while arbitrary are not capricious. They are pretty damn clear. A long gun (rifle or shotgun) is defined as xxx, a handgun is defined as yyy... if neither fits (and don't read into it... is it meant to be fired from the shoulder or not? At THIS moment, not an hour or even ten seconds from now, but right freaking now!) then it's an "other."