This is just a hypothetical. Supposed someone has an AR pistol with a Sig Brace (or some other pistol brace) and they have filed a Form 1 to make an SBR with that lower. Once the Form 1 has been approved and the NFA tax stamp is in hand, is it legal to shoulder that Sig Brace? It's still built as a pistol but it also has an NFA tax stamp to be built as an SBR. So can it be shouldered?
It is far more important to be able to hit the target than it is to haggle over who makes a weapon or who pulls a trigger.
— Dwight D. Eisenhower