IMOThe form is for the SBR you are building now. Not what uppers you may put on it later. So, if you are building a 10.5" 5.56 then put that on the form. Use overall length with stock collapsed.
Therefore you are registering that lower, regardless of what uppers you put on it, which is the reason you can buy several short uppers for one SBR. TrooperBrian honestly did you ask Vader the question and just repost his answer here?
This is the exact advice I would check with ATF before considering.The ATF uses the word intent when talking about what will happen with NFA items.The way I understood Broncovan’s question is he was asking what is the ATF’s view on operating in the gray area outside of what’s specified on the form 1 and possessing multiple short barrel uppers and only one registered lower is definitely somewhere I wouldn’t go without a letter on ATF letterhead affirming I could.One weapon one form 1. Make them match. New form 1 for each new weapon. Make them match. Easy, its only $200 now to keep you from answering awkward questions from the ATF later. Remember when in doubt ask the ATF not us interwebs expert guy’s.
So unofficially, you should be alright as long as
TrooperBrian will you ask Vader a question for me and repost his answer here? a short barreled full auto M-16
I have been trying all afternoon to get onto the ATF website to submit a question about the different uppers for a SBR AR15. Pat
For what it's worth I recently got a form 1 back that had "multiple calibers and multiple barrel lengths" in block h.
"Please dedicate one barrel length and one caliber on you ATF Form 1; after the approved form is returned to you, you may send a letter to the address noted below indicating that you will have interchangeable barrels (provide lengths) and/or interchangeable calibers (provide calibers):
Here is the response from the BATF NFA Branch. It seems like a reasonable request and process."Please dedicate one barrel length and one caliber on you ATF Form 1; after the approved form is returned to you, you may send a letter to the address noted below indicating that you will have interchangeable barrels (provide lengths) and/or interchangeable calibers (provide calibers): DOJ/BATFNFA Branch244 Needy RoadSuite 1250Martinsburg, WV 25405"