Before things went crazy with the election I bought three AR Stripped Lowers from a manufacturer shipped to a local FFL. On the 4473 they where transfered to me as receivers vs. long gun or handgun. My state has no registration and I was not given a copy of the 4473 which is standard I have never been given a copy for a firearm purchase. If I wanted to build an AR pistol from one I think that would be legal. If I am questioned on what I have how do I prove I have not put a short barrel and removed the stock from a rifle? In essence having a non NFA registered SBR. Who would the burden of proof be on? Would I have to prove it is a pistol / not a rifle or would the authorities have to prove it is not a pistol / is a rifle? How would anything be proved by anyone one way or the other? Anyone know?