Originally Posted by
OlongJohnson
My understanding is that if a firearm is first assembled as a pistol, then it can be reassembled as a rifle, and re-reassembled as a pistol as often and as many times as desired.
So if an AR was assembled the very first time as an unambiguous, early-00s style pistol with a round receiver extension and nothing more on it than maybe a foam sleeve, it is eligible to be returned to a legal pistol configuration for all time. It can be made into a standard rifle without filing any special paperwork, or made into an SBR or AOW with a stamp. And you can go back and forth. You just have to be careful of the path you take transiting between states so you don't as an intermediate state assemble a configuration for which you have not acquired a stamp. As in, if you have a stamp for an SBR, don't let it be an AOW when changing from rifle to SBR or pistol.
However, if a firearm is first assembled as a rifle, then it is always a rifle. If a stamp is acquired, it can be reassembled as an SBR, because that is a subcategory of rifle, but it can never be a pistol.
So if this notice starts being used to make determinations that braced pistols are actually SBRs, then they will be and will have always been rifles in the eyes of BATFE.
However, if they were first assembled as unambiguous pistols with non-braced round receiver extensions, and the brace added later, then they could be converted back to pistols. I suppose that in that case, if a stamp was acquired and if the particular brace you used was one that worked with a round tube, rather than a "carbine" extension, you could go back and forth between pistol and SBR configuration simply by removing or reattaching the brace. It seems likely that BATFE will argue that a carbine RE is "objectively" intended to be used with a shouldering device, but it would be much harder for them to argue that a round tube without any additional device attached is "objectively" a stock.
I wouldn't want to go back and forth between configurations by changing the receiver extension, as that means messing with castle nut stakes every time you make a change, and likely a new castle nut and receiver end plate.
As always,