If it transfers as an other, it is whatever you want it to be (rifle, pistol, firearm) if it transfers to someone else later (say you went to the range and someone godfathered you into making a sale, while the gun was in rifle config, and you went to an FFL to do the paperwork) on a 4473, whatever it transfers as, it now is.But the point is, there would be no way to know how the receiver started it's life. Tracing it back to the form 4473 would show it was transferred as "other." There's no way to prove the original configuration one way or another.