TFB Review: C-MORE M26 CMC, Non-NFA MASSterkey

Nicholas C
by Nicholas C

Did the featured image catch your attention? Do you want to know more? Well, come on in. I acquired a somewhat obscure straight pull bolt action shotgun made by C-MORE called the M26 CMC. It is a competition variant of the more popular M26 MASS.

Shotguns @ TFB:


Photo by C-MORE

Some of you may be familiar with the NFA version of the M26 CMC. The M26 MASS (Modular Accessory Shotgun System) is an underbarreled shotgun meant to replace the more common 870 Masterkey. The M26 MASS is a magazine-fed 12ga shotgun. It is manually operated with a straight pull charging handle. According to people online, the M26 MASS has been seen in various first-person shooting games. It has also been used in a small number of action movies.

Well C-MORE made a civilian version, not that you cannot own the M26 MASS but it is an NFA item as a SBS or possibly an AOW. The civilian variant of the M26 MASS is called the M26 CMC and C-MORE claims it is for competition.

How Much Is That Doggie In The Window?

I came across the M26 CMC at my local LGS on consignment. They wanted $1200 and MSRP is $1,399. Not great but not terrible. I was intrigued with making a non-NFA masterkey so I bought it.

The M26 CMC seems to be the same receiver as the M26 MASS. While I do not know what the barrel mount looks like up close, the whole grip/stock assembly is quick detach just like the M26 MASS. This simplifies their production. They just need to attach an 18″ barrel and handguard to make a non-NFA shotgun. The stock is commercial-spec with a thick soft rubber recoil pad. The buffer tube is actually a piston and retracts to help absorb recoil.

Stock removed from the M26 CMC.

When I brought the M26 CMC home, I discovered the 5-round magazines are similar to SAIGA-12 magazines.

C-MORE M26 magazine on the left. SGM 10rd SAIGA-12 magazine on the right.

Look how high the follower sits in the M26 magazine vs the SGM SAIGA-12 magazine. I found that SAIGA-12 mags sort of work in the M26 CMC. They fit but I had difficulty feeding rounds when I tried it with dummy rounds. Later I took the SGM magazines out to the range and the hammer was not hitting the firing pin. Look at the photo below. Look at the left feed lip on the C-MORE magazine. It has a 90º cut in it. Something attached to the hammer hits this preventing it from hitting the firing pin.

I cut the 90º clearance but waiting to hit the range again but dry firing seems promising.

If you haven’t noticed, the M26 CMC comes with a free float railed handguard. It lacks the iconic barrel mount that doubles as the M26 MASS sighting system. I ended up test-fitting the M26 to the bottom rails of railed handguards. I used my ADM dual Picatinny grabber to attach the top rail of the M26 to the bottom of this M4 KAC handguard.

Here is the M26 CMC under mounted on my KAC HK91 handguard.

I used a SureFire 100 to match the absurd length of the M26 with the SGM 10 round magazine.

See how far the rear of the M26 sits away from the magwell and the trigger guard is just hanging out on its own?

Vang Comp, You’re My Only Hope!

Photo by C-MORE
Photo by C-MORE

I originally reached out to C-MORE to see if I could buy their barrel mount parts. See the photos above. The front sight folds down and it attaches to a proprietary barrel mount clamped under the FSB of an M4. Unfortunately, they would not sell me these parts. They are only for the NFA M26. So I reached out to Cody Stewart of Vang Comp. I remember how well their modifications worked on my Magpul edition Remington 870 shotgun. I was hoping he could perform the same modifications to the M26 CMC. Cody was not sure since he was not familiar with the M26. All that mattered though was if the barrel could be removed. Since the M26 is not an autoloader, it is pretty straight forward and the barrel could be removed to be modified. I took the M26 apart to show Cody that it could be done.

The other “key” to making the M26 CMC into an M26 MASSterkey was getting a barrel mount. I did not like the free float handguard and did not like the idea of simply bolting Picatinny rail to Picatinny rail. The M26 receiver and trigger guard are designed to interface with the front of a Mil-Spec AR mag well. Without a properly spaced barrel mount, the trigger guard will swing down. It needs the lip of the mag well to keep it in place and using Picatinny rail grabbers positions the M26 CMC receiver too low.

I found an 870-style masterkey mount made by Armed To The Teeth Technologies. Here is the underbarrel mount mocked up on the M26 CMC.

M26 CMC MASSterkey!

Here are the photos Cody sent me after they finished modifying the M26 CMC.

Vang Comp porting. The forcing cone was lengthened but that is hard to see.

Vang Comp was able to modify the M26 CMC to get the underbarrel mount to line up.

Here are some close-up pics I took when I got the M26 back.

Vang Comp even threaded the barrel for chokes.

One minor drawback is that I do not have an easy way to sight in the M26 MASSterkey. I took an M4 profile barrel with KAC Quad Rail and mounted it to the barrel mount. Is this how a High-Rib sight works? Massive height over bore am I right?

My only problem now is that I did not have a barrel clamp to hold the barrel to the M26 MASSterkey. So I ordered the LMT one. Silly thing costs as much as the underbarrel mount! Both combined cost just over half of what I paid for the M26!

As you can see, the KAC M16 handguard has a cutout specifically for M203 barrel mounts which is what I’m using for the M26 MASSterkey.

Shooting The Modified M26 CMC

I was a little concerned. The gun only weighs around 6.5 lbs. When I first shot it back in February, the recoil was noticeable. The thick recoil pad and spring buffer seem to help a bit. But with the Vang Comp porting and lengthened forcing cone, it is so soft shooting it is amazing.

Of course, shooting it on an M16-style rifle adds significant weight so it dampens even more recoil.

Final Thoughts On The M26 MASSterkey

I am a little disappointed in C-MORE that they refuse to sell the mounts for the M26 MASS. I doubt they are selling that many M26 shotguns aside from the ones already allocated to the military. But I am over the moon about the modifications Vang Comp performed on it. It truly transformed the gun and it worked out better than I had hoped. I want to take it to shoot sporting clays but the clubs that run them are operated by fudds and they have minimum barrel length requirements. The barrel has to be 22″ or longer. I want to have fun and see what this straight-pull action shotgun can do. It is threaded for chokes, I could use a full choke and try to reach out and hit some flying clays.

Another avenue for modification is to find an M203 stock. While the M26 has its own stock, the barrel-mounted M203 stocks would allow me to add an optic to the stand-alone M26 MASSterkey. The only problem is this stock costs as much as the M26!

Photo by LMT

If you want to learn more about the M26 CMC, check out C-MORE’s website.

Nicholas C
Nicholas C

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2 of 30 comments
  • Cap'n Mike Cap'n Mike on Jan 04, 2024

    What a delightful waste of time and money.
    I love it.
    I scratched this itch by bolting a Mossberg 500 to a Colt SP1 ala Billy in Predator.👍

  • Uncle Yar Uncle Yar on Jan 04, 2024

    I just realized something. The Armed to the Teeth Masterkey mount can be redrilled to fit most other shotguns (pump and semi without buffer tube)... And the front QD barrel latch, you can source Airsoft M203 QD brackets for like, 60 dollars, as opposed to 240 something dollars for a surplus KAC QD bracket.

    All in all, 350+60 dollars and a drill press to mount almost any shotgun to an M4 or M16 barrel, that's neat. If it's just for fun and reliability doesn't matter much, source a Stevens 320 (Chinese Winchester 1300) or a Citadel Bosshog to go with it. Hell, get a Maverick 88 for 200 dollars. For under 630 dollars total, anyone can have a non NFA Masterkey for fun.

    For maximum fun, though, I suggest shelling for that stamp and mount a Tac-13 or Mossberg Shockwave on it.