I do not believe that DPMS is chambering anything but a standard chamber. Rock River comes with Wylde Chambered uppers. With that said, my 24 DPMS 1-9 upper is ver accurate. I have shot 3/4" groups at 300 yds with single loaded 75gr Berger or Starke bullets. A-Max do a shade larger, but still less then MOA at distance! Buy the DPMS. I know they caution the use of suprlus ammo!