The previous posters are correct. You can have a short upper on a lower that is registered as a pistol BUT it cannot have a stock. Also, you cannot be in possession of a short upper (less than 16 inches) if you don't have a pistol lower for it. That assumes that you have ONLY non-pistol and non-SBR lowers.
I'm interested in building an SBR and every once in a while I'll see a short-barreled upper that I cannot buy until I have either an SBR lower or a pistol lower in my possession.
I'm interested in building an SBR and every once in a while I'll see a short-barreled upper that I cannot buy until I have either an SBR lower or a pistol lower in my possession.