CMMG MkG45 Guard Rifle – PCC in .45 ACP


Pistol caliber AR carbines have become very popular in recent years. In the majority of circumstances, “pistol caliber AR” has been synonymous with “straight blowback 9mm carbine.” CMMG is now offering an alternative platform that changes this paradigm. It is called the MkG45 Guard.

The MkG45 Guard is a new line of AR-style firearms chambered in .45 ACP. These guns use a delayed blowback system that is said to be better suited for pistol cartridges than straight blowback.

Called Radial Delayed Blowback, the system causes the bolt to rotate during recoil. This system reduces the velocity of the bolt so that powerful pistol cartridges can be used without the need of a heavy buffer system. In fact, CMMG states that these .45 guns use a buffer that is lighter than a standard 9mm buffer from a straight blowback system.

For the end user this results in two things: a lighter gun and less felt recoil. Some people are surprised by the amount of recoil that a pistol caliber carbine can produce – especially in something like a Kel-Tec Sub-2000. This system should tame the rearward force of the bolt.

One potential issue that I am concerned about is that the company offers a bolt weight kit for “…those who wish to fine-tune the Guard for +P ammunition…” I would hope that the gun would run reliably with standard pressure and +P ammo.


There is only 2,000 PSI difference between the maximum average pressure of standard .45 ACP (21,000 PSI) and .45 ACP +P (23,000 PSI.) However, that is an increase of about 9.5%, which could be enough to throw off the delayed blowback system. Once these get into the hands of reviewers, I hope people take a close look at this and see how the gun runs with both pressures.

CMMG designed the MkG45 to feed from Glock 21 magazines. The guns ship with 13-round Glock factory magazines, and the company recommends Glock manufactured magazines for best reliability.

CMMG will offer this gun in five versions including carbine, PDW and pistol models. The base “T” model will have a 16.1” threaded barrel with brake, M4-style stock, A2-style pistol grip and a KeyMod hand guard. Unloaded, the gun weighs only 5.6 pounds. It has a MSRP of $1,299.95.

Richard Johnson

An advocate of gun proliferation zones, Richard is a long time shooter, former cop and internet entrepreneur. Among the many places he calls home is


  • Dr. Longfellow Buchenrad

    I wonder about pistol caliber ARs. If Im going to go full AR, I may as well be shooting a rifle caliber. Other platforms like a MP5 or Scorpion make more sense because they are actually more compact, but an AR pattern PCC just seems to give the worst of both worlds.

    • Holdfast_II

      There are some pluses:

      1) They are more pleasant for use at indoor ranges in the winter – you want the AR manual of arms, but not the concussion that can come from using rifle cartridges in a narrow, enclosed space.

      2) With .45, the round is subsonic, so it can be efficiently suppressed – but the rounds are a lot cheaper than .300BLK.

      3) You can have magazine commonality with your long arm and sidearm.

      4) If you had to use it in a home defense scenario, your hearing damage will be less than if you were shooting 5.56mm.

      All that said, this is primarily a range toy, no denying that. But it looks like a fun one.

      • PK

        A fun range toy as the primary use sounds about right, and that’s just fine by me! It’s one of the aspects of the firearms hobby I enjoy most, that there’s something for everyone.

      • The_Champ

        All good points.
        And lets face the facts here; pretty much everyone at TFB, in practice, uses most/all their firearms as range toys, hunting aside.

        I can already hear them begging to differ, but it’s true.

        • valorius

          My AR556 is my primary home defense weapon. I hope i’ll never have to use it for that.

          • Fox Hunter

            You better be wearing electronic ear pro while you sleep, you will need them when shooting an ar indoors. even a subsonic .300 blk from a 16 inch barrel is louder than 9mm or 45 acp from the same length barrel, and it makes sense as subsonic .300 blk uses more powder than most common pistol cartridges.

          • valorius

            I’ve fired thousands of rounds of 7.62mm linked from an M60 in rooms as small as 10’x10′ in numerous MOUT exercises. I’m entirely certain a half dozen rounds or so of 5.56mm will have exactly zero effect on anything.
            -An ex infantryman

    • PK

      Think of it more as an updated, more modern .45 Marlin Camp Carbine. It has a niche to fill, for sure.

      • valorius

        Or a far less sucky M3 grease gun.

        • Fox Hunter

          Cost wise, it is more like a semi Thompson.

          • valorius

            I’d much rather have the Thompson for it’s awesome historical value.

    • Bean Guy

      In my state, all 5.56/.223 ARs need HBAR profile barrles. Any other caliber is fair game.

      This is why I have a 9mm AR and a 7.62x39mm AR in addition to my HBAR .223 Wylde. The weight matters

      • iksnilol

        Why? What’s the big deal about barrel profiles?

        • JSmath

          Quick google and it’d seem it’s Maryland, in the lines of the usual moronic “assault weapons” train of thought on what makes a firearm scary or not. And apparently so lax that manufacturers are left to their discretion to designate what a heavy barrel is, any profile larger than pencil.

        • Bean Guy

          As JSmath said – idiotic and nonsensical legislature for literally no good reason.

          I personally err on the side of caution since I’m such a law-abiding citizen of my state and actually get true HBAR/Bull barrels for my .223/5.56 builds

          • iksnilol

            I mean, what’s up with the law?

            Is it that pencil barrels are banned as assault weapons or something ?

          • JSmath

            Yes. Supposedly/apparently: “Thin” barrels being legally defined by the specific pencil contour used by manufacturers. And “heavy” barrel” being defined as any contour that is literally measurably thicker and marked as heavy. So the whole ‘it justifies PCC ARs’ isn’t actually true but I’m not going to go out of my way to point out stupid laws in backwards hopes of getting letters or laws rewritten more stringently…

  • PK

    I wonder what the cyclic is with a RLL or RDIAS, if the carrier can be made compatible. I’d like to see how that particular delay works over a high round count, both silenced and not.

    I wish they’d offer just the upper for those of us with .45acp lowers, although I understand why they haven’t done so yet.

  • Spencerhut

    Having a long gun that uses the same ammo and mags as your sidearm is not a horrible idea. The main benefit being the ease with which you can get solid hits out to 100-150 yards compared to a pistol.
    I’d still rather have just a .223/300 rifle and leave the pistol behind rather than lug two guns that use under powered ammo.

  • Ark

    All the disadvantages of a pistol caliber, only it’s a caliber that costs more than .223. Thanks, no thanks. Hard to come up with a more pointless gun.

    • GD Ajax

      AR fanboys will buy it no matter how expensive. Sucker born every minute and all that.
      The frugal gun buyer will pass on it for a real sub machine gun.

  • Anonymoose

    *cue Keymod haters*

    • USMC03Vet


  • iksnilol

    1300 for heavier ammo, less range and much higher ammo cost?


    y’know, a regular 700 dollar AR.

    • JSmath

      But .45ACP has that knock down power that 5.56NATO completely lacks.


    • Alexandru Ianu

      Subsonic PCC for surpressed fun times.

      • iksnilol

        Yeah, but isn’t the name a bit misleading then? I don’t visualize guards using suppressed .45s.

        • JSmath

          If I was a guard and indoors or moving a lot, and had the option to run a subsonic compact SMG/PCC, I’d definitely strongly consider it.

    • valorius

      Forget $700, you can get a brand new Ruger AR556 for $450 nowadays.

      • iksnilol


        So yeah, you can buy an AR, kit it out, buy some ammo and still have money left over.

        • valorius

          Since Trump won companies have dropped their prices to awesomely ridiculous levels. 😀

          • Fox Hunter

            A new AR-15 renaissance. Cool.

          • valorius

            It really is. You can build an entire AR rifle kit for less than $400.

  • Big Daddy

    I have a QC10 .45ACP AR15 pistol. It runs great on any ammo. The glock mags work fine as do the later SGM mags I have. I also have a Kriss mag but have some issues with it. I use the QC10 BCG and barrel with a KAK extra heavy long buffer. It shoots SP and +P ammo without issues.

    The biggest issue is muzzle flip. I studied ballistics and chose a 5.5″ QC10 barrel, longer barrels did little to increase velocity. So it’s a short handy powerful gun. Now how do I handle the rise and flip? I tried a Lonewolf Glock muzzle break, it made it worse and would be better off with a thread protector which really surprised me. Since it has an odd thread I was limited. On my QC10 9mm AR pistol I have a very expensive Lantac Dragon, it works amazingly and I wish they made one for the 45 thread which is .578 x 28. Next I tried a 4 1/2″ long KAW valley linear comp, well it worked a little better but added a lot of length.

    So I am interested in that muzzle break. I’ll wait until they eventually sell them or someone does as this type of gun becomes more popular.

    But the idea of a proprietary design and parts kills it for me. Plus the price. Either make it gas or direct blowback, especially if it has to be tuned. What happens if I want to add a suppressor. SInce the bolt already rotates make it a gas system and make it also in 10mm. A hybrid recoil rotating bolt system sounds like it is very dependant on tuning and timing.

    • Fox Hunter

      A gas system will be more complex and expensive compared to a delayed inertia system. Gas systems have to be tuned and timed as well, especially when you are not using standard powders with standard burn rates. Remember this is a PCC, and the Reising SMG has proven that delayed inertia is ideal for heavy pistol cartridges like the .45 acp in carbines or SMGs, better than either direct inertia/straight blowback or locked breech gas systems, at least with regards to the gun running smoothy without having a very heavy bolt, the MP5 with its roller delayed blowback system also shows this. Personally i would prefer direct inertia/straight blowback, if you can handle the recoil from a subcompact .45 acp, a blowback carbine in the same caliber should be no problem.

      • Big Daddy

        Gas system 45 ARs are already out there and proven. They work.

  • Ryfyle

    Why not use a short stoke gas system if theirs so much pressure? Also, why not use 10mm Auto? I’m also getting the feeling that regular AR expansion system would have also worked, but that dosen’t allow for the price now does it.

    • Fox Hunter

      Flint River Arms already has a short stroke AR-based PCC, it was even at Shot show 2017.

      • Ryfyle

        Neato. Seems like there making it in all the fun flavors, like 10mm.

  • 22winmag

    I’ll take three Sub2000 .40’s and a case of ammo please.

  • J

    RJ, will CMMG be developing this platform in other calibers as well?

    • I’m afraid I do not know. I would imagine that the company would be happy to do so if the demand is there. If you want to see this in 9mm, 10mm, etc, give them a call: 660-248-2293. They definitely need to hear from their customers.

  • Brian Fulmer

    As I’ve just picked up 250 lead 238 gr bullets to load up for 300 BLK for my wife to swap to from her Mossberg 500, this is a useful innovation to my mind. Deafening and possibly blinding yourself in a self-defense scenario in your home is a terrible idea inadvertently advocated by those folks who insist 5.56 NATO is the end all be all for self defense. Heck, I REALLY like 357 Magnum and 357 SIG, but a shotgun and a 45 are way better choices for indoor use. In comparison, a 556 is even WORSE!

    A smart operating system that minimizes recoil and is EXPLICITLY compatible with +P 45 ACP = smart niche move. My wife’s 300 BLK may get an upper-ectomy.

    • Fox Hunter

      Agree! I’m a big fan of smgs and pccs, especially in sbr/ braced pistol/ cheekrest pistol forms. I consider them ideal for home defense, way better than tilting barrel handguns or shotguns.

  • Fox Hunter

    Wow, that sounds like a system developed a hundred years ago, or more, by Ferdinand Mannlicher or John Thompson or Pedersen. This is cool, problem is they went with single feed mags, again. They should have used thompson smg mags, double feed>single feed, if they were going with single feed mags, it should have been grease gun mags. Handgun mags work in handguns, not so much in carbines, again double feed mags>>> single feed mags.
    SMG mags >>> handgun mags.

  • Deej S

    How about a 460 Rowland ar?