Scot’s Product Review: CMMG Mutant Mk47 AKM

If you like the 7.62x39mm Russian cartridge but aren’t a fan of the AK47 or SKS, CMMG may have just the rifle for you. At first glance it looks like an AR, but the second look tells you something is different. They call it the Mutant because, while it uses a lot of the basic AR platform, both the upper and lower receivers are unique as they were re-sized for the cartridge and to use the AK magazine. In other words, it is not a standard AR by any means though some parts will interchange, like the trigger group, safety, and stock. It does, however, operate much like an AR, other than changing the magazine.

The Mutant answers the need for a more potent weapon than the AR15. Many feel that the cartridge native to the AR, the .223 Remington/5.56x45mm NATO, just doesn’t hit hard enough. While the round has dropped many a target over the last 50 plus years, there have been many stories of failures. The round started off touted as an amazing killer in the early days of Vietnam with stories of ripping enemy soldiers into shreds. These effects were usually attributed to the bullet yawing, tumbling, and fragmenting through the target. We later, however, heard stories that it was a failure when it didn’t do those things and all you got was a neat .22 caliber hole that didn’t impress enemies very much. The failure stories grew as time passed. New loadings, like the M855 with a 62-grain bullet that replaced the original 55 grain M193 load, appeared to fail far more often. Complaints from soldiers in the Blackhawk Down street battle in Mogadishu in 1993 confirmed to many that there was indeed something wrong.

Shortening barrels hasn’t helped. The AR originally had 20-inch barrels, but the current M4 has a 14.5-inch one. Even shorter barrels are used for special purposes. Every shortening of the barrel means lost velocity, which reduces the likelihood that the bullet will yaw on impact.

Curiously, according to Army surveys on weapons, while one soldier is very happy with his weapon and ammunition, the next is terribly disappointed. One line of reasoning for this conundrum surfaced in reading about Dr. Gary Roberts’ work on the Internet. Roberts is a dental surgeon and Navy Lt. Commander who has spent a lot of time researching wound ballistics. He is a consultant to many governmental organizations and shares some of his work with the rest of us. He noted that while some M4’s will stabilize the bullets better than others, some bullets are less likely to yaw on impact. With no yaw, you get a marginal wound.

Another issue has been performance through barriers, such as auto glass. Small, fast, light bullets often end up passing through barriers, and bullet bits don’t do much to bad guys. Shooting into cars came up a lot in the Middle East, where the car bomb is a weapon of choice.

Some argue that loading it with the right bullet is the answer, and there has been a lot of research to develop better ones. Some researchers look for bullets that don’t need to yaw on impact, while others look for bullets that yaw and tumble reliably. One of the new loads the MK262 with a 77-grain match bullet is used by our special ops troops and anyone else who can get them. While they still have problems getting through barriers, the commentary from the war zones has been very positive on their performance. There are also bullets designed to pass through barriers and still hit hard enough to do damage. These include the MK318 Special Operations Science and Technology (SOST) round with a 62-grain bullet. Reports from the Mideast say that it has been used effectively by Marines in combat and is now their round of choice.

Besides improving the .223 cartridge, there have been a number of efforts to get more powerful cartridge with larger bullets into the AR. Two results have been the 6.8mm SPC and .300 AAC Blackout. The 6.8 developed out of a military desire to get as much reach and impact from the AR platform as possible. The .300 round focused more on optimum performance in short-barreled rifles and the ability to use subsonic ammunition for quiet operation with suppressors. The .300 Blackout has acquired a devoted following among hog hunters.

Both rounds appear to work well and have strong supporters. The chief problems both face is scarcity and cost. While both function in a standard AR receiver, they obviously require new barrels. The 6.8 also needs a different bolt and magazines. If you could easily get ammunition, especially low cost stuff for practice, I think these rounds would be far more popular.

One other drawback with the Blackout is that a few people have managed to chamber them in .223 rifles. The results are not pretty. After I pulled out the firing pin, I tried it in the DRD Tactical I reviewed last year and the bolt would not close, but this was with factory ammo and crimped bullets. If a bullet weren’t crimped or the case had weak neck tension, the bullet might be pushed deeper into the case and the cartridge could chamber. This scares the dickens out of me, and I try to avoid having a .223 and a .300 AAC in operation at the same time.

There is, however, another cartridge that many think ideal in this size weapon; it’s the 7.62x39mm Russian used in the SKS and AK47. It hits harder than .300 Blackout by about 200 feet per second (FPS) to boot. The problem has been getting it to function in the AR, which was made for a smaller, differently shaped cartridge. You have probably noticed that the AK magazine has a lot more curve than the AR magazine. This has to do with the cartridge being tapered more than the .223 Remington. Trying to feed the 7.62 through an AR-shaped magazine has not been completely successful, and the AR magazine well precludes adding more curve to the AR magazine.

Another problem is the bolt. The case head of the Russian round is much larger than the .223, and when you mill out the bolt face to take the 7.62 you are left with a lot less bolt. That affects the robustness of the rifle.

One might ask why not just toss the AR and get an AK? That’s a good question and certainly a good answer for many. I recently spent a fair amount of time with an AK and found that many of my prejudices towards the weapon were unfounded. That said, I find the ergonomics of the AR much better for me, particularly the operation of the safety. I also think the AR design is more accurate, which was born out in this test. We can debate how much accuracy one needs in a defensive rifle, but in the end it is sort of like money. It is hard to have too much, though we don’t want to compromise ourselves to get it.

Oh yeah, there is also the matter of optics. Putting them on the AK is expensive and many mounts don’t hold zero. That’s a huge advantage for the AR.

The idea of an AR that shoots 7.62×39 is appealing to many, however, and CMMG has overcome the two key issues– the magazine and the bolt– by building an AR-based rifle with unique parts to provide robustness and function.

The key to solving the magazine and bolt issues was new upper and lower receivers. Stock AR15 or AR10 receivers simply can’t take an AK magazine and if they were to make the bolt the optimum size for the Russian round, the AR15 one is too small, and the AR10 one is longer than necessary. It is the same sort of problem Goldilocks faced with porridge. She wanted it just right and so did CMMG.

CMMG, therefore, designed new receivers to take a shortened AR10 bolt carrier group and the AK magazine. They used computer numerically controlled (CNC) machines to make them from a billet of 7075-T-6 aluminum. This means taking a solid chunk of forged aluminum and using the machines to cut away everything that isn’t receiver. AR receivers are usually forged into the shape of the receiver by beating on hot metal. They then receive relatively minor machining to make them into guns. Forging receivers, however, requires a lot of serious industrial equipment, and there are very few companies in the U.S. equipped to do it. Getting someone to make the unique receivers CMMG needed by forging would have been very expensive, and CNC offered a way to get them at reasonable cost.

People argue a lot about one process being better than the other. Some say that a forging is stronger, while others poo poo that point and note that a CNC receiver can be more precisely made than a forging. The forging backers counter that while tolerances matter, forging is good enough and they point to all of the fine AR’s made their way. I’m of the mind, after reading arguments from both sides, that either process can make excellent rifles. The one point I will give the CNC folks is that the finish is usually prettier on their products and they can easily incorporate things like flared magazine wells or just more style if they feel like it.

One of the great things about the Mutant is that it takes a lot of standard AR15 parts, including the fire control group. If you want a different trigger or safety, just head to your favorite dealer and ante up. It also uses standard AR furniture.

Once CMMG solved the receiver problems, they turned to the bolt carrier group. Like the receivers, it is a hybrid. It uses the bolt from an AR10 to get the diameter they feel is needed for reliability and strength, while the AR10 carrier is shortened to no longer than needed to function with the cartridge. They could have simply put it in a full-sized AR10, but then they would have had a heavier, bulkier rifle. Since they brought the whole thing in at 7.2 pounds, I think they did a good job. It is a rare AR10 that is this light, and I have handled a lot of AR15’s that are heavier despite shooting a weaker round. It is also lighter than most AK’s which run close to 8 pounds.

The Mutant is well equipped out of the box, though it lacks iron sights. Many users will want a specific sight, so rather than hang something on it you might throw away, CMMG leaves it up to you to get what you want.

I really like the excellent 15-inch KeyMod handguard CMMG uses. It is made of a lightweight aluminum alloy and has a full length Picatinny rail on the top that lines up with the one on the upper receiver. There is plenty of room for your scope and sights exactly where you want them. The front sight can be almost at the muzzle, extending sight radius to improve accuracy. There is plenty of extra space for lasers or night vision if you have them. On the sides and bottom are rows of holes on which you can hang a number of KeyMod accessories.

KeyMod, by the way, is a shared standard created by Vltor Weapons Systems and brought to market by Noveske Rifle Works. Vltor and Noveske placed the standard into the public domain, and other companies jumped on the bandwagon making products that can share attachments. This was of great benefit to users and generous of Vltor and Noveske. The idea is to have keyhole-like slots cut into handguards that can be used to attach accessories. This makes for a far lighter system than covering the handguard with Picatinny rails. It is also more comfortable to hold onto.

The two main things you will probably put into those slots will be an attachment point for a quick detachable (QD) sling swivel and some strips of Picatinny rail for a light and switch. Some versions of the CMMG handguard have QD holes present, but this one didn’t. You can also get adapters for bipods and grips. By only adding enough mounting points for what you actually need, you save weight and make the rifle sleeker to handle.

One thing these handguards don’t do as well as the old fashioned ones is protect you from heat, but you can get lightweight covers to shield you.

The handguard free floats the barrel, which means it transfers no pressure to the barrel from the sling or the hardware you hang on it. This may or may not make the rifle more intrinsically accurate (I think it does but some don’t); it does make it more consistent. Pressure on the barrel can affect where the bullet goes, and if you vary the pressure you get different points of impact. Heating can also affect consistency, and again a free floated barrel will react more consistently.

The stock is a very nice Magpul MOE. It is comfortable and works well. I find them harder to get off the rifle than an issue one, though. You have to kind of pull while poking into a catch to get it off, but it doesn’t have to come off very often.

The pistol grip is also Magpul MOE, and I like the way it feels. It has a storage compartment to hold stuff, and there are optional inserts to hold specific things like batteries, spare parts, or lube. I wish the compartment cover was retained to the grip, however. Since there are interchangeable covers to hold different items, they have to be removable, but I’m clumsy and drop stuff in the dirt. A detachable strap might be good to retain it.

One thing the Mutant shares with its AK sibling is the lack of bolt catch. Apparently the communists felt their troops didn’t need to be warned they had run dry by the bolt locking back, so they left that off. That means the magazines don’t provide a means to put this feature into a rifle that uses them. I wish, however, there was a manual bolt lock back, as sometimes it is nice to lock a weapon open. Many ranges desire just that during target change times.

Another problem is that when you run dry and get a click, you have to run the bolt to chamber a new round. That takes more work than hitting the bolt release on an AR and gets us to one feature I think CMMG really needs to work on. The charging handle is the same size you find on a stock AR and is for right-handed shooters. The larger shape of the Mutant receiver further complicates the matter so it is harder than the one on a standard AR. You can replace the latch on the handle with a larger one, but since the Mutant has a unique length charging handle, you can’t just dump it and upgrade to an ambidextrous handle.

The trigger on the sample I’m reviewing is the best trigger I’ve encountered on an AR. It is 5.5 pounds, which isn’t light, but it is clean and crisp, which makes it very manageable for a defensive or hunting weapon. It’s the first AR I’ve handled that didn’t make me want to immediately send money to Geissele for a new trigger. If all of them are this good, praise be.

The gas system is direct impingement, just like normal AR’s. That means gas goes directly into the bolt to start things moving. Many don’t like this, as it puts dirt into the action. A piston gun would keep fouling out of the action, but at the cost of more parts and weight. I’ve listened to target shooters explain that the less mass you have bouncing around, the more accuracy and consistency you can get from a rifle. I use both types of rifles and find either to work well, though I prefer cleaning a piston gun. It is not a deal breaker for me either way.

The barrel is 16.1 inches long to keep it from needing federal approval and has a muzzle brake fitted that worked well at reducing muzzle jump and recoil. This is at the cost of more flash and blast, however. If it were mine, I would probably eventually get around to replacing it with a flash hider, as I hate blast and flash. It would bounce around more, but I don’t find the recoil of a 7.62×39 bothersome. One needs to consider their own priorities on this point, of course.

So how does the thing shoot? Quite well, in fact. I tried seven loads and was very pleased with accuracy. I used my Leupold Vari-X III 3.5-10x50mm set at 10x at 100 yards in an indoor range. Groups were analyzed with OnTarget software, which allows you to scan a target and input the location of the bullet holes. It then computes the center to center distance from the two that are the farthest apart. This measurement is what we usually see when people talk about group sizes. It also gives us the average to center, which may be more useful as it tells us how far from our aiming point our shots will land on average. It then provides the group height and width, which can tell us if there is a pattern other than round. I would like to have perfectly round groups, but I often see tall or wide ones instead.

The Winchester PowerPoint was the best load I tried for accuracy, and it was nice to find it is well regarded for hunting and self-defense. This is brass cased, reloadable ammo.

The second best was Silver Bear soft points in steel cases you can’t reload, but when you can find it, it is usually quite inexpensive. I haven’t found much information on its effectiveness for hunting or self-defense, however.

The groups gradually widened from that point, and the worst was only 3.4 inches center to center, which is quite acceptable accuracy for a defensive carbine. I was hoping for better from this load, however, as it is the Hornady SST in steel cases, which makes it fairly cheap and it is well regarded for hunting. I had a flier in both of groups I fired, which badly affected the numbers. It is possible I pulled the shots, but I thought I was doing okay, so I left them in. Without the fliers, this would have been the most accurate load.

I shot two five shot groups with each load and used the worst for the report.


Besides shooting off the bench in an air-conditioned range, I took it outdoors in the hostile southeastern heat and humidity and blew through about 300 rounds running drills. Other than magazine changes and a bit more recoil, it was much like running an AR in .223. I found magazine changes slower and more awkward than with an AR. The AR magazine drops when you hit the release, and the new one goes straight in. If the bolt is locked back, you hit the bolt release and go. With the Mutant or AK, you have to push a lever that hangs down behind the magazine and rock it out. You then rock in a new one and if the gun has been run dry, run the bolt.

To me, it is clear the AR is simpler to reload, but it is also clear from watching good shooters handle AK’s that the time gap can be small. Skill matters the most.

I was slightly slower on splits with the Mutant due to the recoil, but that is to be expected. Since you are hitting harder, you probably don’t need to hit as often.

One issue that came up was that this rifle did not like the steel communist magazines I have. They are Bulgarian, Polish, and Rumanian. They all worked well in an AK, so there is some issue with them and the CMMG. The Rumanian magazine does not want to go in at all. The Bulgarian will go in partially loaded, but the more rounds you put in it the harder it is to seat, and at 30 rounds it is almost impossible to get in. The Polish magazine would seat, but I had six feeding failures. CMMG’s spokesperson assured me the rifle is intended to work with all AK magazines, so I presume this is a problem with this individual rifle and these particular magazines and that CMMG would take care of it. This rifle was not new and had been through the hands of several other writers and that might have been a factor. If you are buying one over the counter, it might be a good idea to check if this matters to you. Some other reviewers have had no issue with any magazines, while others have also identified individual magazines that wouldn’t work.

On the other hand, it was absolutely perfect with the polymer Magpul MOE magazines that came with it and a Tapco 20 round polymer magazine. If it were me, I would be very, very happy with the Magpul ones. They are lighter than steel and won’t rust. My steel ones started rusting on the way home from the range the first time I used them (and to be fair, sweated on them.)

I was very impressed with this rifle. It is making me do a lot of hard thinking about defensive long guns. I have always enjoyed shooting the AR, and as the system has gotten more modular and easier to adapt to one’s needs I have grown very fond of it. I think the 7.62×39 hits harder at the ranges most of us can realistically require for self-defense or hunting. A .30 caliber bullet simply makes more sense to me for medium game. I’m looking back and forth between the CMMG and my AR’s and wondering if I should make a switch.

The only drawback to the Mutant is price. Getting it right wasn’t inexpensive. The base model Mk47 T goes for $1,499.95 list. It is basically the same gun as the Mk47 AKM tested here, but has a standard AR stock and pistol grip rather that the upgraded Magpul furniture. The Mk47 AKM lists for $1,649.95. The top end Mk47 AKM2 adds the very nice Geissele SSA trigger and goes for $1,849.95. All three models get the excellent handguard. I do note that they can be found for about $200 less on Gun Broker.

It would be easy to justify getting the entry model and upgrading later as it wouldn’t cost anymore and would give you some spare parts. You can, however, get a decent AR or AK in the $500-700 range these days. If you are just starting out on your defensive battery and like the 7.62×39 cartridge, you could always get an AK, a bunch of Magpul magazines, and ammo and upgrade to the Mutant later, and either sell the AK or keep if for a backup. If you value accuracy and ergonomics, you will be drawn to the Mutant.

– SurvivalBlog Field Gear Editor, Scot Frank Eire