We like the KeyMod handguards and it takes AK magazines. Yet, so does the Rock River and MGI, What makes the CMMG different? Why all the recent hype?
The main difference is in how robust the Mutant is and how they achieved this. The upper receiver is larger than an AR15 but not as long as an AR10’s. The bolt carrier has the dimensions of an AR10, in girth, but tapers to a 15’s in the rear of the BC. The buffer is proprietary, though it will function with an AR10 carbine buffer, they’ve given it a different weight.
In standard 7.62x39mm AR conversions a 5.56mm bolt is used and widened to the 7.62’s circumference. This makes the lugs weak and they do break. Below on the right you will see CMMG is using an AR10 sized bolt to really improve the strength. Though this does result in a proprietary barrel extension.
Buyers have asked for a better 7.62x39mm AR platform and often disappointed with what they are sold. The trade off here is in a lack of interchangeable parts but a retention in most of the muscle memory of AR use, not to mention the superior optic mounting platform of an AR system.