Possibly the best ar upper receiver out there - Vltor Modular Upper Receiver

I now have 3 of these. The first 2 I purchased to build "accuracy uppers" with. One is a 6.8 with a White Oak 18" barrel and shoot's 1/3" groups with several loads. The other is a .22 Nosler upper with an Odin Works 18" bbl that also groups under 1/3" with several different loads. The quality of these uppers and the attention to detail is just great. I firmly believe the extra thickness and heat and cryogenic treating that Vltor does to them creates a perfect foundation for an ultra high quality build.

The third one of these uppers I purchased just to upgrade the receiver so my 6.8 carbine because I had put a Wilson Combat barrel on it, and I just felt the regular old mil spec upper it was wearing just didn't do it justice. :-) They are that nice.