SBR lower reporting requirements

[rxer311]

I got my Form 1 for my SBR a few months ago and have been building another upper for it (which I have a pistol lower for as well...which will also eventually have a form 1 sent in for). In the mean time, I would like to put my new upper on the SBR lower. Do I have to report to the ATF that I will be using the lower in a different configuration with a different barrel length? If so, is there a form I have to fill out or how do I do it? I thought I was good to go as long as I kept the upper for the orginal config, but I was informed by a local gun store and associate that I trust that I really should report to the ATF. Is this just being extra cautious, or is it required?
Thanks.

[alamo5000]

My understanding is no you don't have to report it. That said the advice I was given was to keep the original upper nearby just in case.

[gatordev]

No. If you want to report the change, just send a letter. But keep in mind when reporting it, you're either a) reporting a PERMANENT change to the NFA item (ie, a different upper) or b) you're reporting an additional configuration (something the ATF won't let you do on the F1, which is silly, and leads me to believe they don't care).

If you sell the original upper (or more accurately, the actual barrel), then I'd recommend sending a letter notifying of a the permanent change (ie, change in barrel length on the "new" upper).

[Stone]

Once the lower has a stamp you can swap out uppers to your hearts content, no need to notify. You can put a 2"-20" barrel on it and change them out 50 times a day, it doesn't matter. They recommend if you go over 16" to notify because it takes it out of the NFA status but even then I wouldn't waste my time since I would be putting a shorter barrel back on it sooner or later.