Quoted:
So I have my stamp already. When i built the SBR I purchased a 7 in upper. Now i run a 10.5 inch always. Can i sale the 7 inch upperi never use it.
Box E on application says 7 inch   Box F says Overall 26.5

Quoted:


yes you can.

you just need to notify the ATF in writing of the permanent change

Quoted:


You actually do not need to notify ATF nor should you here. Selling the upper is not considered permanent. Only irreversible physical modifications to the firearm itself are considered permanent and even then notification is optional. You are free to use your SBR as you wish.

Quoted:


To piggy back...
I have a F1 pending for a 10.3" 556 upper
Found out my wife is prego so I doubt I'll be buying that upper any time soon. When I get my F1 back, can I have my CMMG .22lr upper cut to NFA length and not have to worry about notifying the ATF about caliber/length change? So in essence, run a 12.5" .22lr upper on a registered lower that the F1 says 10.3"/5.56 without having possession of a 10.3"/5.56 upper?

Quoted:
Anyone else want to chime in ?
I know i can use other uppers on my SBR lower but i thought i had to keep the original 7 inch

Quoted:


Technically speaking, you should build your SBR in the configuration listed on the Form 1 first. Once that is done, your SBR is "made" per the Form 1 application and you are free to change calibers and barrel lengths as often as you wish.  I would suggest you use someone else's 10.3" upper and install it as soon as your Form 1 is approved, then remove it. Done and done.

Remember, the Form 1 is strictly for making the SBR, it does not govern the use of the SBR thereafter.  Think of the Form 1 as a birth certificate for your SBR.  In the same way you are not forever limited to your birth weight and height shown on your birth certificate, your SBR is not held to its initial build configuration.