I wanted to put together my own version of a DMR so I looked through the options from FNAR, DPMS... to scoping my M1A. I decided to go with a 20inch AR10 A4 last week and got it to the range yesterday. It has a Burris Signature Select 1.5 x 6 x 40 with Burris XTR high rings. I was using Remington 150's for sight-in. Let me say it took about 6 shots at 50 yds and 6 shots at 100 yds to get her dialed in to 1 inch group at 1.5 inches high. This gun is heavy-ish but a pure pleasure to shoot. It functioned flawlessly, barely recoils and is accurate. I add one mistep becuase I didnt seat the magazine fully. It was expensive and I am going to have to Gunbroker some stuff but it appears to be a winner! I am always excited/nervous about the first sight-in ever since I had a $$$$ DSA para-FAL break on the 6th shot! I was never able to trust in again.