TFB Review: CMMG MkGs Guard 9mm AR-15

    MkGs Guard

    The CMMG MkGs Guard 9mm AR-15 has been formally announced to the public, and we at TFB were extremely fortunate enough to have the opportunity to range test and review this firearm. Let’s take a look at the specifications of this rifle and what we exactly have on our hands here.

    • BARREL: 16″ M4 4140CM SBN, 9mm
    • MUZZLE: CMMG SV Brake, Threaded ½” x 36 T.P.I.
    • HAND GUARD: CMMG RKM14 Keymod Rail
    • FURNITURE: Magpul MOE Pistol Grip, Magpul CTR stock w/ 6-Position Mil-Spec Receiver Extension
    • RECEIVERS: Billet 7075-T6 Aluminum Lower, Forged 7075-T6 Aluminum Upper
    • TRIGGER: CMMG Single Stage Mil-Spec Style Trigger
    • MAGAZINE: Glock 9mm 33-Round
    • WEIGHT: 6.2 lbs (UNLOADED)
    • MSRP: $1,399.95

    To put this rifle through its paces I brought along 300 rounds of ammunition from 3 different manufacturers with 4 different flavors.

    MKGs Guard

    The ammo that was tested was as follows:

    • CCI Blazer 9mm 115 Grain FMJ (Aluminum Casing)
    • CCI Blazer Brass 9mm 115 Grain FMJ (Brass Casing)
    • Fiocchi Shooting Dynamics 9mm 115 Grain FMJ (Brass Casing)
    • PMC Bronze 9mm 115 Grain FMJ (Brass Casing)

    The optic that was used, although unrelated to the success or failure of the MkGs Guard 9mm during this review, was a Vortex StrikeEagle 1-6x24mm scope. An accuracy test of the rifle was not performed during this review. I do not think people should put a lot of weight or thought in my ability to shoot a rifle (or lack there of) if they are contemplating buying the MkGs Guard 9mm from CMMG.

    MkGs Guard

    While cycling through the 300 rounds that were brought to the range for this review, there were a couple things I noticed. This rifle was very smooth shooting. That was very noticeable from the outset. After speaking with CMMG more about their MkGs Guard they said that feeling of a smoother operating rifle is coming from the Radial Delayed Blowback system that this new rifle operates on.

    To expand on that further, the Radial Delayed Blowback system that CMMG is using in the MkGs Guard rifle is something brand new and exclusive to CMMG. A traditional blowback designed 9mm rifle versus the Radial Delayed Blowback of the CMMG has a significantly different bolt-carrier group (BCG). The mass of the Radial Delayed Blowback BCG is 6.4 ounces LESS. This nearly half pound lighter BCG is great for those desiring a lighter rifle.

    MkGs Guard

    As the video more quickly explains above, the Radial Delayed Blowback mechanism features a BCG where the back of the bolt is chamfered. As the bolt begins to spin and unlock, energy is burned up throughout this blowback process. This allows the rifle to utilize a lighter buffer and spring. It also equates to a lower recoil impulse. When you add all these things together, you get a smoother operating rifle and a silly grin on your face from ear to ear.

    I also noticed that the rifle was fairly smokey to shoot. We are not talking muzzleloader smokey, but it was noticeable. This can be attributed to the fact that there is no gas tube to this rifle like a standard AR-15. All of the smoke, gas and fine debris is ejected through the ejection port of the receiver as opposed to going through a carbine, mid-length or rifle-length gas system of some kind.

    MkGs Guard

    All of the ammo that was shot through this rifle in a relatively short period of time performed flawlessly except for the CCI Blazer (aluminum casing). Towards the end of the 33-Round Glock magazine that CMMG provides with this rifle, a round would fail to clear the ejection port and would subsequently get crushed by the bolt as it reciprocated forward. This occurred on two different 33-Round Glock magazines within the last 3 rounds of the magazine being empty; 2nd to last round or 3rd to last. Surprisingly, never the very last round.

    Something as quirky as this I do not believe is fair to attribute to the rifle. The magazines may have not had consistent spring tension or an even follower riding up. It is important to note that the 250 rounds of brass-cased ammo I brought to the range never experienced this; only the CCI Blazer (aluminum casing).

    MkGs Guard

    One feature of this rifle that I did not get to enjoy is attempting to shoot it suppressed. The muzzle brake on this rifle came off easily enough with a wrench, but it had a very fine thread pitch. It was not your standard 1/2″ x 28 TPI you would expect with a 9mm. Instead, it is 1/2″ x 36 TPI which is much more fine. I later learned from CMMG that their reasoning for this is to stay true to how Colt 9mm rifles were originally threaded. With that different thread pitch, range enthusiasts will not unknowingly slap on their 5.56mm silencer (1/2″ x 28 TPI) and blast a new 9mm hole out the front. I completely understand their reasoning, but I was still disappointed because the Silencerco Hybrid .46 Cal silencer I own could have fit… if the rifle were 1/2″ x 28 TPI.

    This is merely something to take note of for future owners. If you search silencer companies and their selection of rear caps for their products most will offer a 1/2″ x 36 TPI attachment.

    MkGs Guard

    Something else to take note of, but is not necessarily a hindrance to this rifle is the upper receiver. When you remove the upper assembly, take the charging handle and BCG out you can see a hole at the front of the upper receiver. The reason why the hole is there is the upper receiver is a standard AR-15 configuration. While the MkGs Guard does not employ a gas system that requires a gas tube that hole is still present. There is a remote chance debris could enter through this hole into the action, but it is very unlikely. By CMMG choosing not to plug that hole it likely saves the consumer money; less inherent build cost using standardized, readily available machining and parts.

    To round out the rifle, it is always a good baseline to see Magpul furniture. It fits my hands and shoulders well for me so I appreciate it. If it does not personally suit you it is very easy to switch out to your favorite preferred brand.

    I am also a part of the Keymod bandwagon so I liked the sleek rail this rifle was equipped with. Once again, you could completely disagree with me, but switching out a rail is fairly simple as well if that does not trip your trigger.

    MkGs Guard

    A small mark against the MkGs Guard is the fact that the castle nut is not staked. This may have been purposefully done by CMMG because like my prior statements it allows the end user to modify the gun to his/her liking. By the gun not being staked and this only being a 9mm, it definitely does not compromise the integrity or functionality of the rifle.

    The last point I will touch on is the magazine release button. You can see in the photo above that it is huge! So whether you are shooting with gloves, have small hands or are all butterfingers at the range during a match, you should have zero problems manipulating the magazine release on this rifle.

    MKGs Guard

    I mentioned a lot of detracting, indifferent and positive points about the CMMG MkGs Guard 9mm AR-15 throughout this review. All in all, I believe it is an extremely fun and smooth shooting rifle. Light recoiling, great curb appeal and you have the easily-found Glock magazine compatibility working for you.

    Given the opportunity and room in your gun safe I would not hesitate to add the MkGs Guard to your collection if you are in the market for a 9mm rifle.




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