Re: Rock river uppers stainless 8 twist barrels??
I have the 20" Predator Pursuit and it does well with 75 grain bullets. Just be sure to run something heavy in it and you should have great luck. The price is very competitive. I don't have the quad rail, just a pic mounted to the bottom of the factory free float tube for an Atlas but that is essentially irrelevant. You can expect sub MOA accuracy if you do your end of things. I think most people that have this upper would say the same thing. I take guys out all the time that never have shot a rifle and they easily hit a 5" steel target at 500 yards in the correct conditions given that I give them the proper instruction.
I'm running a DPMS lower with the RR two stage match trigger, and I'm not overly impressed with the trigger. If you like a light pull I would probably advise a nice single stage. I would say you can buy with confidence. Just my two cents.