CMMG Mutant 1,000 Round Follow-Up Test

After sending his MK 47 Mutant back to the manufacturer following its failure in a previous 1,000 round shooting session, Mrgunsngear has gotten the rifle back from CMMG, with a new locking compound applied to the gas block. Naturally, it’s time for another 1,000 round test, to see how the new setup holds up:

The rifle passed this time, with two failures to feed, each with a separate Tapco magazine, and each with rounds in a similar position in each magazine. It’s pretty understandable that in the wide variety of different AK magazines available, some would work and some would not, especially with a totally new rifle that has its own feed geometry different than an AK’s. The fact that the magazines that failed were commercial magazines, and not military ones subject to more stringent specifications, is further unsurprising. I don’t feel those two failures reflect all that negatively on the rifle itself.

No word yet if the new locking compound will be put on all future CMMG MK 47 rifles. My personal preference there would be for staked screws, but the locking compound is clearly a major improvement over the old Loctite that was being used on the gas block in the first test.

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Andrew Hobby

    If only there was some *Crazy Super-Rifle* with the reliability of the AK… hmmm….

    • Cal S.

      With all the aftermarket components available for AKs that can effectively turn it into an AR (or thereabouts) for about half the MSRP of these rifles (including base AK plus furniture, ambi charging handle, co-witness optic mount, trigger guard mag release, etc.), it’s almost an exercise in futility to make guns like this. But, the market will determine that.

      • Dave

        i’d have to disagree with how they milled this bolt from an ar10 bolt. I’ve seen too many pics of converted 15 bolts with sheared lugs

    • M

      There are problems with the US AK market. An AK clone that can actually live up to it’s legendary reliability is actually quite rare: Single stack bolts, barrels built to non-soviet standards, poorly riveted rifles, the list goes on and on, and is present in even boutique rifles like Arsenal SLRs. “Properly built” is actually expensive and rare.

    • CommonSense23

      Even the AK can’t live up to the supposed reliability of a AK.

    • Esh325

      I’m not really sure the 7.62×39 is really a suitable round for the AR system to begin with. The .300 BLK might be more expensive, but it’s honestly a better solution for a platform designed primarily around the .223.

      • Cornelius Carroll

        The mutant is designed around the AR-10 (iirc) which is a native 7.62×51 platform.

  • JQPub

    Going to have to watch the video when I can. The (nomex?) glove on his left hand has me a little curious of course

    • JQPub

      Ahh ok. I get the glove thing now. Damn, that was one hell of a torture test. It really stood up well to all those rounds in that short order, all in different mags. I’d hesitate to think how well an AR 5.56 would hold up under those same conditions. Think it probably would have flamed the gas tube and possibly seized up the bolt/BCG. That was pretty impressive

      • some guy

        Seeing as the MK47 uses the same operating mechanism as a standard AR15 I’d imagine they’d hold up about the same. 7.62×39 has a bit more taper to it so it might extract slightly better in the presence of really heavy fouling but beyond that I don’t think you’d see much difference.

  • Kivaari

    Why would they need a new compound on the gas block? Shouldn’t it be pinned in place? Guns help together with “glue” where heat is so high, seems like a poor design. I’ve never seen a good AR pattern rifle needing such a compound on the gas block. I did have LEO Colt 9mm AR15 that had the barrel unscrew at the wrong time. It did not have a gas tube that limited the barrel nut to be kept in place. Colt’s repair people were discourteous and down right obnoxious about it happening.

  • UKShuggy

    I cringe during these YouTube torture tests when I see people chambering a really hot gun that is pointing at the sky. Does the possibility off a cook-off never occur to them?