Let's say that I have purchased an official pistol registered lower reciever. Let's say that I have an extra complete 9mmm carbine upper half with a 16 inch barrel. Can I legally cut down the carbine upper barrel to 10.5 inches and run this upper  assly on the pistol registered lower? If so, who could legally cut this down and rethread the barrel for me?

I have heard ADCO does tremendous work on refitting barrels.

ADCO did the one on the left. It started as a RRA 16'' upper. They are simply the BEST!

Lumberjacker- thanks for the info and pic. That is what I needed to know. Please tell me what buffer tube and buffer you have on your 9mm pistol in the photo.

Quoted: Lumberjacker- thanks for the info and pic. That is what I needed to know. Please tell me what buffer tube and buffer you have on your 9mm pistol in the photo.

Check this thread in the EE.

http://www.ar15.com/forums/topic.html?b=7&f=125&t=288231

The tube from RB Precsion will let you use a rear retainer plate ( needed to hold the rear takedown pin detent and spring in) and have enough threads to catch the buffer retainer. You can get the retainer plate and the ACE pad from them also. You will have to remove a small amount of material from the raised portion of the retainer because it wont slide over the threads. The standard carbine stock tube has a slot milled in the bottom for the raised portion of the retainer plate to slide on and keep the tube lined up in the correct position. I use a RRA 9mm buffer and a standard carbine recoil spring.

Ditto on ADCO. He cut down a 16" 9mm upper to 10.5 for me works great. As long as it's a pistol lower run what ever length barrel you want just DON'T put a rifle butt stock on it unless you've got a 16" plus barrel on it. Once it's registered as a pistol it can be used as a pistol or rifle with PROPER CONFIGURATION. But a registerd rifle lower can not be used as a pistol.

David