I actually got a chance to play with that "thing" in Vegas, before it hit the market.... NOT pleased (which can be expected from a sub-par company) The receiver, barrel extension, bolt and carrier are all proprietary. I believe the handguard may be too. The sized up the parts somewhere between the AR15 and the 308AR. They [CMMG] believe the problem with the original design was the fragile bolts.... Except that LMT and Cason Eng are claiming THOUSANDS of steel cased rounds on the same bolts.... in full auto!!! It wasn't a bolt failure, it was a metallurgy failure. The new bolts are not made from tool steel. The Mk47 Mutant is overweight, unsightly, bulky in uncomfortable locations, and all around a fix to a problem that no longer exists. If you had to buy a rifle TODAY, and you wanted something from over the counter.... The POF or the PWS would be my only suggestions. If you wait till the end of this year.... I PROMISE YOU WILL SEE AN ALL NEW 7.62X39 RIFLE DESIGN. I can't speak more on that right now, but stay tuned.