After seeing the noveske build by dennysguns, I've come to the conclusion That I want one of those little Bastards. I have a few questions before i get busy.
A) What kind of accuracy will the 10.5 produce at 100yrds?
B) How much velocity is lost by being 5.5in shorter?
C) I've allways heard of reliability issues with 10.5, is there a special set up that solves these problems?
D)In the area of the paperwork, I know it has to be rejistered as a SBR. Can you build the upper first and then rejister a lower, and complete it when it is approved?
Or, does the paperwork have to be approved before getting started at all?
Thanks, any helpful answers would be greatly appreciated.
Reaper

A) Sub-MOA
B) About 300 FPS versus a 16" barrel
C) The Krink brake or a piston helps.
D) Technically you don't want the upper around the house.  Constructive possession and all that.

Thankyou asu1911 for the answers

c) Run a H2 buffer and a Wolff Extra Power extractor spring and you’ll be fine. Like ASU1911 said, a Noveske Krink will also help.

300 fps for a 10.5" vs 16" barrel? More like 400 fps.  Also some 10.5" barrels are listed as 10.3" such as LMT which is in actuality 10.25" in length.  Too short to mount an M4-2000 on where the 10.5" would fit.  Just something to keep in mind.