12.5" Upper, Nice Lower. What is this tax stamps you speak of!?


Well, I’m really wanting to go full on SBR and have some fun either at the range, or in some classes. Build idea would be a BCM complete lower, and top it off with a BCM 12.5" complete upper w/a MS4D flash comp.

So to stay out of the clutches of John Law, am I correct in getting the lower first, then submitting a form 1 on the lower having it changed to a SBR, the slapping the 12.5" upper on and being good to go?

Do I need another stamp for the upper or will anything still be an issue being under 16.1" in barrel length? Just want to keep on the right side of the law.



I want a SBR, but not willing to pay the tax stamp and wait. Instead, I got a bullpup.


Isn’t it a Form 1 wait? I thought those were pretty short. I’d rather pay for just a lower and wait for a bit than pay for a full damn rifle and wait for a year+


No waiting on a bullpup. Barrel is still 16" and over all length is the minimum legal.


Bullpups are as short as an SBR or shorter but still compliant to the 16" barrel rule. Really they are a great alternative with superior ballistics to an SBR.




Another thought: you could build it as a pistol with a brace, do your paperwork, when you get the okay, change the buffer tube and stock. Voila SBR


Please, correct me if I am wrong, but when you buy an AR pistol, is the gas tube length pistol instead of carbine?


No , I think there is a pistol length but most people keep it all standard and just run pistol buffer set ups.


Your gas tube will match whatever the barrel is drilled at…pistol, carbine, midlength, or rifle length. I’m going to guess that the upper you are referring to is already assembled, so it’s something you wouldn’t have to deal with at all.

The buffer tube on a pistol build is essentially exactly the same as a carbine buffer tube…except it will not allow the use of an adjustable carbine stock.
So when you get your okay from ATF, you would only need to change out the buffer tube and add your stock. The inner parts (spring and buffer) will be re-used so no need to purchase them.


Isn’t it a short wait time for the Form 1 e-file though?
I have other things I can shoot for a month if it’s just a short time, but it may be nice to keep a pistol lower and brace so I could cross state lines of the opportunity presented itself.


I actually have no idea on ATF wait/processing times. Maybe someone else can chime in.

I have a feeling that if you go the pistol route (with a good brace) you’ll find the need for an SBR kind of evaporate…spend the saved $$$ on a real good brace :wink:

I was considering the same thing until I built my first pistol AR…now there’s no thought in my mind about going the SBR route…


On AR pistols chambered in 5.56mm, the pistol length gas system is common for barrels around 7 to 8 inches in length. With 5.56mm pistol barrels 10.25 inches and up, the carbine length gas system is common.

I’ve got a few braces, and the SB3A is my favorite, so far.

I haven’t jumped into NFA paperwork myself, but from what I’ve been hearing, the wait seems to be a matter of rolling the dice. Some people get the stamp in 2 or 3 months, while others are taking a little over a year.


I have honestly never really liked any AR pistol with the brace, or maybe I just have not had a brace that I felt good about on an AR.


Times are all over but have seen some people still posting up 17 and 23 days to be approved. I have pistols and sbrs. I much prefer my sbr and stock. As cheap as lowers are now. Build one to go across state lines and one for in state classes.


You only need to file and pay the tax for the lower. However, don’t be in possession of the upper until you have the stamp back and in your hands. This will avoid any issues of constructive intent.

Best of luck with your build.