If I wanted to build a pistol kit (postban config, Kevlar lower, <50oz total) onto my former-rifle lower, how must I proceed?  Does the new firearm now somehow have to be registered as a "pistol"?  From what I can tell, current restrictions abound on the "purchase" of handgun receivers, but not the "conversion" of a rifle into a pistol.  BATF couldn't consider it a non-compliant SBR, since there wouldn't be a buttstock, and with only 2 evil features with weight under 50oz, it should be a legit pistol.  Help!?

Rifle-to-pistol conversions are a no-no.  Register it as a pistol when you first buy the bare lower & you're off to a good start.

Norm_G is correct. Pistol to rifle conversions are ok, but not vice versa. Once a rifle always a rifle, just like machineguns.

I have a question on another angle on the AR pistol/rifle thing.  How do you finish off an 80% lower and designate it as a pistol/rifle????
Are 80% lowers only sold as "80% rifle" lowers?

Who's keeping track of that aspect and how would you stay out of trouble????

www-2.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/atf_letter7.txt