I'm looking to rid my collection of all but one .223/5.56 rifle and move to the much better 6.8. I had a friend build this .223 upper for me way before I knew how easy a upper was to put together. It was a 16" bbl cut down to 13.7" and rethreaded, then pinned a piggy on the end to meet the 16" OAL. I don't know the brand/twist/chamber of the bbl since there are no markings, it should have been a Colt though. I have shot 5.56 though it without any pressure signs on the spent brass. I do know it is a M4 pencil contour and has M4 ramps. The reciever is a key hole forged with M4 ramps also. The BCG is a Stag. The CH is a standard mil spec. The HG is a Vtac rifle length and has a lo pro gas block. If you like to hunt with a .223 AR out of a deer stand, this upper is nice due to the short length, plus the pig helps wiith the sound and recoil.
The only problem I know of on this upper is the builder grinded one of the notches down on the bbl nut so the gas tube would line up. Why he did this, I don't have a clue other than even with the right torque it would still not line up. However, it is a tack driver using Hornady .223 V-Max 55gr. That was 5 shots at 100yds with a 4X Acog.
I've ran maybe 300 rnds through it and used a bore guide for cleaning. $600 shipped and if you feel it is not as described, send it back for a refund.
If you have a ARP or Bison 6.8 upper you would be intrested in trading, let me know. If it is a Bison, I'd like to have the blasted or black finish. Other 6.8 brands might be considered but it needs to have the right chamber and twist. SPC II and 1/11. thanks