Rock River Arms - "Varmint" bull barrel 1:8 twist complete upper.
This upper comes with the factory RRA bolt and carrier, and has a Badger extended charging handle. Just snap it on your lower, and go target/varmint shooting!
It shoots the Winchester white box 45gr, BH52, BH68, and BH77 stuff VERY well. It has the Wilson 1:8 stainless bull barrel, with the Wylde chamber.... which gives incredible accuracy with NATO spec reliability. This is the most accurate upper I have owned. I imagine it has around 600 rounds down the tube. These are $610 new from RRA.