One Way The CMMG Mutant Is Different

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Partially as a result of the AK’s success, non-Kalashnikov designs utilizing the magazine of the 7.62x39mm Avtomat were few and far between until very recently. Due in part to civilian demand, in part the needs of special forces, and in part to countries armed with aging 7.62mm AK rifles looking to replace them – but not their magazines and ammunition, which are often still in production – there has been something of a resurgence of designs based around the venerable 7.62x39mm cartridge and the tough-but-heavy AK-pattern magazine.
At the 2015 SHOT Show, as Troubleshooter Berlin and I were wandering the floor, he mentioned that the magazine wells of some modern designs provided insufficient or improper support to the magazines. Naturally, we decided then to seek out as many of these rifles in the show as possible and compare them. While we were able to take a look at all the ones we could remember, in a few cases I did not have the presence of mind to take photographs, so this article will be supplemented with photos taken from the Internet. First, and most important is the AK rifle itself. This firearm supports its magazines in six areas: Front, rear top, rear bottom, each side, and the front top, indicated below:

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Picture showing the support areas of the AK magazine. The part that most concerns us is indicated by the red lines. Image source: Troubleshooter Berlin.

The front and rear supports are most obvious to a designer of a new firearm using these magazines; also evident is that the front sides of the magazine where it is reduced in diameter also need support (not indicated in the above picture). What’s often neglected, we found, was supporting the top of the magazine, indicated in red in the above image. How does the AK magazine support this area? A view up through the magazine well will show us:
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Highlighted in red, the two wings that support the AK magazine against tension and over-insertion. These are critical areas for proper functioning. Image source: akfiles.com, modified by author.

Next on our list is the SIG 556R, one of the rifles of which I did not manage to take any pictures:

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SIG did not have any AK magazines at its booth, so I was unable to see how the raceways shown here interacted with the magazine. However, it’s evident that they don’t reach in as far as the “wings” on the AK’s trunnion, and further, as they are straight and extend all the way to the rear of the magazine well, they cannot support the top front of the AK magazine, which is stepped down. Image source: reddit.com.

The Rock River LAR-47 is a similar rifle to the CMMG MK 47 that was announced three years ago:
2015-02-09 22_13_38-SHOT Show 2012_ Rock River Arms LAR-47 Rifle - YouTube

This somewhat dark image – a still taken from a video – shows the inside of the magazine well. No support is apparent, but a different angle may be called for. Image source: Guns & Ammo’s Youtube channel.

2015-02-09 22_10_07-Rock River LAR47 7.62x39 Rifle Shot Show Review - YouTube

Another screencap – blurrier, but the lighting is better. The lack of support is evident in this shot. Image source: modernpawn’s YouTube channel.

Another AR-15 offering that supports the use of AK magazines, the MGI Hydra multicaliber rifle:

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The MGI Hydra uses a modified pattern of AR-15 upper receiver when using the AK magazine well. As a result, it does not provide the correct support for the top of the magazine.

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The extra relief needed for AK magazines to fit is evident in this photo.

Finally, the CMMG MK 47 Mutant:

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Two “wings” in the upper receiver protrude, showing the support given to the top of the magazine by the MK 47’s upper receiver. Further, wear is evident on the PMag-AK’s top front surface, giving proof that the MK 47 is supporting the magazine as it should.

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The MK 47 properly supporting the magazine in its receiver.

These pictures make one thing clear: Among the non-AK designs utilizing this pattern of magazine shown here, the MK 47 is the most well-designed with respect to magazine support. Is the demand for this sort of rifle great enough that CMMG’s attention to detail will win out over its competitors? It’s difficult to know, but I’m sure owners of the MK 47 will appreciate it, anyway. EDIT: I emailed Brandon Novotny of CMMG about this, and he had this to say:
“The “wings” are most definitely magazine supports. They keep the front of the magazine from pivoting upwards during firing and have nothing to do with guiding the rounds into the chamber. The radii cut from them was necessary in the machining of the feed ramps into the upper.One thing to note that not many people notice is the benefit of the LR308 barrel extension. It has wider feed ramps in it compared to an AR15 which allows the round to more easily feed into the chamber. I’ve seen some AR15s have issues with the M4 feed ramps being too narrow for the larger case of a 7.62x39mm.”


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 can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Riot

    Its not amazing that the mutant does this.
    Its amazing so many others don’t.

    • That was my thought, yup.

    • iksnilol

      You pretty much took the words out of my mouth. I mean, aren’t you supposed to look at the original rifle if you are going to make a rifle that can take its magazines? Seems like common sense to me and I am not even an engineer.

    • 360AD

      Probably one of the reasons some Sig 556R owners experienced issues.

    • n0truscotsman

      Think of it as the cure for scurvy way back in the day

      *hey! we discovered a cure for scurvy!

      (mankind forgets)

      **hey! we rediscovered the cure for scurvy!

  • ManBear

    Does $1600 – $1700 seem a little steep for one of these, or am I just a tight ass?

    • Dracon1201

      Quite steep considering an Arsenal SLR107-FR is going for $900 these days and doesn’t need to use a buffer tube.

      • Scott P

        And it won’t choke in less than 1000 rounds which Arsenal’s or any AK in general won’t have any problem accomplishing still asking for more.

        • Do you have any evidence that the MK 47 couldn’t do the same?

    • Ben

      My AR-15 cost me about $1500 all in. If this rifle is of a similar quality to the AR that I built, I could justify that price. After all, street price is likely to be more in the $1400 range. I don’t understand why people think that guns should be cheap just based on the caliber they are chambered in.

      • Scott P

        What about the design when the AK is a more durable and reliable design than the Mutant but people think the AK should cost $100 and get insulted when priced anywhere near an AR?

        • Ben

          Hi-points are also very durable and reliable. There are many metrics that must be used to judge a firearm, not just durability and reliability. Also, I don’t think there is enough information on the Mutant yet to really compare it to the AK, or any other rifle for that matter. I’m looking forward to learning more about it though.

    • Snozzallos

      No, you’re not a tightwad. It’s merely a big fish in a very small pond of limited or substandard competition. The mutant could very well be worth that $1600 price tag, but there shouldn’t be any reason why it couldn’t be produced at much less cost and still work well. Because magazine support is hard?

      Erm, okay.

  • Fritchof

    I looked at a Mutant at Cabala’s, it was in the $1400 range. I found it to be quite heavy, and not really able to justify the price over a well built AK pattern rifle.

    • iksnilol

      + don’t forget that it uses the AR charging handle *shudders*

      • The AR charging handle has lots of advantages, it’s just that none of them have to do with manipulation.

        • iksnilol

          Good way to put it. It works well enough if you have LSHO (Last Shot Hold Open) but otherwise, I am not a fan. Couldn’t one make a LSHO system for the AK mags too? I mean, you got the Yugo mags with the tab. Couldn’t one make a mechanism to engage the LSHO when the bolt hits the tab or something?

          • I imagine that Yugo mags would hold the bolt open on a Mutant, until you removed the magazine.

            Nobody at CMMG has said anything to me about this, but I have a strong suspicion that they designed the upper to be multi-purpose, not just specific to the MK 47. It is perfectly sized for 2.5″ long cartridges, if a new lower were made for it.

          • iksnilol

            Those at CMMG be like: *whistling innocently*

          • MrGunsnGear has shown that the BHO magazines work with the Mutant.

          • iksnilol

            I thought along the lines of making the bolt stay open after removing the magazine. Could that be done using the existing BHO mags.

      • Tom

        Its funny they set out to solve the “problems” and then left the one of the worst/easily correctable problems of the AR in.

        Now in fairness its not the worst design out there but there are better options.

        • What do you mean? Besides the troubled SIG 556R, all the other alternatives in the MK 47’s class use the same charging handle design.

          I agree it’s not ideal for the purpose, but I suspect it was a design compromise.

          • Tom

            I mean they wanted to improve the AK hence the AR ergonomics but they kept the AR charging handle rather than say use on patterned after the FAL. Of course it should be said that the AR approach is probable the easiest (patent free) approach to make it ambi which is an improvement over the AK right hand side affair.

          • toms

            If they changed the charging handle people would have griped that its not an m4 style. See JP adding the unnecessary traditional charging handle after receiving numerous complaints about the original. Left side charging makes 100% sense and the AR’s rear entry location is the main criticism I have of the rifle. I work around it and still think its the best overall system available today.

          • Dave

            That’s the gen 1. The gen 2 that i owned suffered from none of these problems.

          • Scott P

            Yep Nathaniel needs up to update himself on the Gen 2 556R, that video is dated.

          • I’ve heard they’ve gotten better, but I think the adjective “troubled” is still applicable.

      • Michael Acuna

        Or a side charging method like on the JP Enterprises riles.

        • iksnilol

          I don’t understand. Are you saying that it can use an aftermarket side charging method or that it should have a side charging method?

          English is my 3rd language.

          • Michael Acuna

            It should have one.

  • For the record, I was unable to examine two other similar weapons: The Knight’s SR-47 and the Colt CK-901. Neither were present at SHOT Show 2015, to my knowledge.

    • Tom

      Is the SR47 in production or planned to be. I was under the impression it had been shelved after SOCOM decided they were not interested.

      • Not so far as I know, but I’d still like to take a look at one.

  • Those do not look like “supports” to my mind. With the aforementioned front and rear lug the magazine is fully seated and supported across all three axis. From a mechanical standpoint, those do nothing extra.

    What it does look like is expanded bullet guides to assist with keep the shoulder of the larger case from getting dinged up or otherwise mis-aligned in the chambering process.

    • I don’t see how the bullet wound be guided by those extensions, as they don’t extend beyond the profile of the magazine.

      Unlike an AR-15, the AK does not give its magazines much support. Clearly a rifle can function without the wings, but is denying the relatively unsupported (especially on the top!) magazines the support they would have in their parent rifle really a good idea?

      • When the round clears the rear lips, it will do so at about that point that the shoulder is even with or just past those “guides”. Based on the photos shown, they have radius deferring to the chamber. If it was just “support” why the radius?

        To your other point, they don’t serve as any kind of support on the magazine during normal firing. They would only “support” the magazine when pressure is applied directly from below like when using the magazine as a makeshift bi-pod.

        • The radius is there because that’s how the upper is machined out, mate.

          When pressure is applied directly – as in during normal use? Magazines are generally kept locked in, so there are more conditions of concern to a designer than just during firing, right?

        • John Daniels

          “They would only “support” the magazine when pressure is applied directly from below like when using the magazine as a makeshift bi-pod.”

          Or when doing pushups off the rifle, with a magazine inserted, as the Russians seem fond of doing. Without those supports inside the rifle, I doubt they’d have been able to make that such a routine activity.

          Maybe not strictly necessary for the firing functionality of the rifle, but it did end up becoming important at some point, at least for that reason.

        • Michael M

          You are incorrect. During firing, recoil drives the rifle rearward rapidly. The inertia of the magazine would allow it to pivot on its rear supports, loading the front top supports that Nathaniel pointed out. These top supports appear designed to support this load during normal firing. Even more so if the rifle magazine is resting on a stationary surface while firing.

  • toms

    I wonder if the Swiss 553R, ck901, ARX160 have support wings?

    • Good question; I don’t know.

      • iksnilol

        Well, could you find out? I mean, you guys have access to more hardware than me. At least modern stuff.

        • As previously mentioned, none of those rifles were present at SHOT to my knowledge, and they’re not exactly available at my local gun store, either.

          • iksnilol

            Good point… What about Alex C.? Does he have any access? Not a pressing matter but it is interesting… + I am a bit jealous of all the stuff you guys get to try/buy. Sure, I have access to firearms from WW2 and the 90’s and whatnot but I don’t have much access to the newer stuff.

          • I think the latter two have yet to be released on the civilian market.

  • It seems like an excellent rifle, but for the money I’d go with an Adam’s Arms 7.63×39 upper piston AR. AK mags are great, but why go DI with that round?

    • DI works fine; there’ds not really any corrosive 7.62×39 about.

  • Richard Wyse

    I think if they charged $1500-1600 AND had a side charging capability, then this would be a great rifle.
    Or just the ability to use any standard latch.

  • It is supported in all directions with the existing two points of contact. All the other rifles mentioned function just fine with the magazine used as a monopod.