Hello everyone,
   Sorry is this question has been asked about a 1,000 times before.  I currently have an AR15 and love it.  I was considering building an SBR, but this is a major pain in the a*s.  The only difference between an AR pistol and rifle that I can see, is that there's no buttstock, but it still has the buffer tube assembly sticking out.   But if you remove the buffer tube assembly, how do you tell an AR pistol lower from a AR rifle lower?

What legally differentiates an AR pistol and a AR rifle, (since the actual receiver itself looks the exact same to me)?  

Also, can I legally add a SBR upper assembly to an AR pistol without the pain of BATF registration?  

Thanks

First build of the lower determines what the lower is from that day forward.  You buy a new stripped never assembled lower as mentioned in the above tacked letter, do the 4473 as anything but a "rifle" lower, assemble and document into pistol form with no stock and <16" barrel and then it is a pistol.  You can never have a butt stock on it in pistol form but if you have a rifle length upper then you can put the rifle length upper on and a stock and go to rifle form, then back again to pistol whenever you want.  Just do NOT ever have the stock on the weapon when the <16" barrel is on the lower.

If the lower was first assembled into a rifle then it is a rifle forever and to make a pistol sized arm out of it the lower must be SBRed.  


The SBR is the lower, not the upper.  Any upper on a pistol lower is legal regardless of length but for simplicity let's limit pistol uppers to less than 16 inches.  If the lower is a rifle lower then to put on the shorter than 16 inch upper the lower must be SBRed first.   There is no difference in a pistol upper and an SBR upper other than the lower they are going on.

Big-Bore,
   Thanks, that cleared it up for me

Quoted: Big-Bore,    Thanks, that cleared it up for me

+1  

If it weren't for the NFA we wouldn't need to know all these differences.