I own 4, two .223 Rem. , one .308 Win, and one .243 Win. all DPMS. I wont tell you they are the best, but I like them; The two I have spent the most time with developing reloads, 20" stainless bull barrel in .223 Rem, and the .243 (actually a remington R25 made by DPMS) can both shoot 5 rnds. at 100 yards and just not quite cover with a dime. I`m not sure what `alot of rounds down range` is equal to, but have close to a couple thousand through one of them and no problems with it.
ETA- Rock River Arms has some nice offerings also.
When chosing a mount for a scope I have used both RRA and Burris (PEPR) mounts, and I like the Burris better.