I apologize if this is an FAQ, but I searched and could not find an answer to my specific question.

(Important note: assume these are brand new and neither of these two firearms ever had a shoulder stock from the factory)

My understanding is that it is legal to do the two following things:

1) Replace the pistol grip of a PGO shotgun (like a +26" OAL factory Mossberg Persuader) with a shoulder stock as long as the barrel is longer than 18", making a non-NFA shotgun

2) If you have an approved Form 1 and tax stamp to make it an SBS, you can replace the birds head grip with a shoulder stock on a +26" OAL "firearm" (like a Mossberg Shockwave or Rem Tac-14) to make an NFA shotgun.

My questions are, can you undo these?

1) After the conversion of shotgun #1, what does it become when you remove the shoulder stock and replace the OEM pistol grip?  If it's still over 26" and has a >18" barrel, but no longer designed to be fired from the shoulder, is it still shotgun or return to being "firearm"?

2) If you have the SBS tax stamp for shotgun #2, is it legal to remove the shoulder stock and replace the OEM Shockwave/ birds head grip?  What will it become if still over 26" but < 18" barrel? Is it still an NFA shotgun or return to being a non NFA "firearm"?  If it remains a shotgun, does an SBS have to retain a shoulder stock?

Thanks for the reply.

OK #1 makes sense though ridiculous since it was fine as OEM before the stock was attached, but I get that's how the idiotic law reads.

I'm still confused about #2 though. You start with a "firearm" built on a virgin receiver. You Form 1 it and get the SBS stamp. You attach the stock. A bit later you remove the stock and put the birdshead on again. You still have a tax stamp. How is it not legal? What is it now?  How could you be charged with an illegal weapon?

Although it can't be a firearm again, once it's a SBS, you can pretty much do whatever with it, no?

Except cross state lines without a 5320.20.

Interesting. Are there any other configurations that are prohibited for a SBS?

Thanks BigWaylon.

This make sense. I get that putting a stock on it or making it shorter than 26" OAL puts it in the NFA, but I couldn't see how you could run afoul after that if you had a stamp for it.

Although I realize you do have to be careful with "makes sense" and the NFA.