Hello. I’m looking to do my first SBR build. Looking at a 10.5 for my first. Is it ok though to go shorter on another upper and switch between the 2. I’ve heard it’s ok to have as many uppers as you want on a single engraved lower, but can one actually be shorter then what your paperwork says.
I figured it would be ok, but a buddy said he spoke with someone at the BATF and they said something along the lines of going shorter is a bad idea
Thanks in advanced
It’s all a gray area, but your buddy is right in telling you going shorter is a bad idea.
Going longer might be alright, but I’d still write a letter to the ATF saying you made such changes.
But this sounds like you’re wanting to be able to switch back and forth?
That brings up a question if you can apply for a stamp for a rifle of barrel lengths from 7.5" to 10.5" all on one stamp. I Don’t know if the ATF would accept that.
Knowing from experience though, if you have a 10.5" you’re most likely never going to shoot the shorter one. The shorter one won’t be nice to suppressor baffles, and unsuppressed it will rattle your teeth from the percussion…it’s a waste of an extra upper and a high risk for something hardly used. Just get the 10.5" and shoot away.
I put 10.5 for my barrel length and routinely swap stuff around. BATFE wisdom says if it is a PERMANENT change you must notify.
Every time they harass me and toss my house they don’t even bother to look.
I was thinking about doing a 8" 300blk in the future. I wouldn’t go shorter then 10.5 on 5.56, but iv heard you can get away with it on the 300blk. Because its still effective and reliable.
You can put any upper, any barrel length you want on a registered lower without notifying anyone as long as you retain the parts necessary to return the rifle to the configuration that’s on your original paperwork.
It is amazing the amount of stupid, wrong information NFA brings out in people.
Note:
Please, stop “messing” with the batfe. If you look at the information available on this site, you will find what you are looking for. Do not write any more letters to the batfe.
If I would have read just a little more carefully, I would have had my sbr papers months ago.
I agree 1,000%. People still haven’t figured out after all this time that just because they “speak” to “someone” at the BATFE it doesn’t mean that they know jack shit about guns or even their own regulations.
I call and write the ATF every day with stupid questions. It’s just a hobby that I get great enjoyment from. 
Last letter I wrote to them was about upgrading my U238 modulator…