I have one. It works great. However, it isn't $2000 better than a Colt M4. The rifle (HK 416) was intended for use with a 10.5 inch barrel, because the DI guns (Colt) didn't have enough push to cycle reliably with a very short (10 inch) barrel. Accuracy for an MR556A1 would be on par with a Colt 6940 (free float barrel) IMHO.