Thanks for your input. My biggest confusion is whether these milsurp receivers are considered "rifle" or "other" on the form 4473. I can legally buy a rifle but not an "other". For instance, I can't buy an AR-15 lower receiver even though I can buy the rifle (and strip it down and sell it until I have the same receiver
).
On the other hand, when my mom and I got my dad an M44 for Father's Day (I picked out a barreled action to drop in an aftermarket stock), our FFL told us either one could have done the transfer because it had already been made into a rifle rather than an "other".
That one was a little clearer because the barrel was still attached. I'm murky on the other stuff though. A receiver once in rifle formation is considered always a rifle, correct? So any receiver that's been attached to a rifle is still considered the rifle, but any virgin receiver is an "other" because it could technically become a pistol? That's my understanding.