CMMG Guard 45 ACP Semi-Automatic Carbine

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

UPDATED December 15th, 2017



CMMG MK-9 T 9x19mm Semi-Automatic Carbine

by Jeff Quinn

photography by Jeff Quinn & Boge Quinn

March 4th, 2014


Click pictures for a larger version.





Top to bottom: bolt release, safety, magazine release.





Top to bottom: dust cover, case deflector, forward assist.





Flash suppressor.



Charging handle.



Six-position buttstock.



The AR-15 is the most popular style of rifle in the US right now, and has been for quite a while. There are numerous makers of such rifles, with more added each month. It used to be that I knew of every manufacturer of the AR-15 without looking at any list, but today, I don't even try to keep track of the number. While the majority of AR-15 rifles are chambered for the popular 5.56x45mm NATO cartridge, there are several other chamberings available, as well. One such chambering that has been available for many years is the 9x19mm (9mm Luger), and in a carbine, the 9mm is a very useful cartridge.

CMMG has been in the AR business for a few years now. My first knowledge of CMMG products was of their offering a 22 LR conversion for the 5.56mm AR-15.  They now offer complete rifles, and this MK-9 T is one of their latest carbines. In addition to this semi-automatic MK-9 T, CMMG also offers other versions of a 9mm carbine, including a short-barreled PDW.

The MK-9 T wears a sixteen inch M-4 profile barrel, made of 4140 steel. The handguard is their RKM11 KeyMod free-float aluminum unit. Being of blowback operation, there is no gas system, but the MK-9 T uses the spring in the stock tube to return the bolt into battery, just as does a direct-impingement or gas-piston AR. The buttstock is of the six-position M4 style, and the flash suppressor is the closed-bottom birdcage configuration. The receiver is forged of 7075-T6 aluminum, for those who are concerned with such details.

The Mk-9 T comes with one thirty-two round steel magazines, which feed from a two-column staggered position. The magazine inserts straight up into the mag well, and locks into position, using a standard AR-15 style magazine catch. The magazine well is properly formed into the lower receiver, instead of just having an after-thought magazine well block, as is sometimes encountered on other brands.

The MK-9 T weighs in at six pounds, four ounces on my scale. It balances well, measuring only thirty-two inches in length, with the buttstock in its shortest position. The MK-9 T has no sights, but wears a Picatinny top rail on the upper receiver, which extends also the full length of the handguard. There is also a short section of rail to attach elsewhere on the handguard, if desired. The trigger is a standard milspec unit, but the trigger pull was much better than what is usually found on a milspec trigger, releasing crisply with four and three-quarters pounds of resistance, as measured with my digital trigger pull scale.

I fired the MK-9 T carbine with several types of 9x19mm ammunition to check for reliability. I also fired a variety of ammunition over the chronograph to check velocities, with the results listed in the chart below. Velocities are listed in feet-per-second (fps). Bullet weights are listed in grains. JHP is a jacketed hollowpoint bullet. DPX is a hollow nose homogenous copper bullet. FP is a frangible, pre-fragmented flatnose bullet. FMJ is a full metal jacket roundnose bullet. PB is Cor-Bon Pow’RBall, a specialty hollowpoint bullet with a polymer insert to insure expansion and to prevent the hollow nose from clogging with clothing or other material. XPB is a Barnes homogenous copper hollow-cavity bullet. Velocities were taken at an elevation of 541 feet above sea level, with an air temperature of twenty degrees Fahrenheit and seventy-eight percent humidity. Accuracy was tested at a distance of fifty yards, firing five-shot groups with the CMMG carbine rested in a Target Shooting, Inc. Model 500 rifle rest, with a Leupold 8.5 to 25 power Mark 4 scope attached atop the receiver rail.

Ammunition Bullet Weight Velocity
WCC NATO FMJ 124 1233
Buffalo Bore +P+ JHP 124 1367
Buffalo Bore +P+ JHP 115 1656
Buffalo Bore +P JHP 147 1123
Buffalo Bore +P+ XPB 95 1678
Cor-Bon +P JHP 115 1357
Cor-Bon Pow’RBall 100 1414
Cor-Bon +P DPX 115 1289
Federal Guard Dog 105 1307
Remington Home Defense 124 1221
Atomic +P JHP 124 1444

Reliability of the CMMG carbine was excellent. Every cartridge fed and fired flawlessly, with the exception of a Remington hollowpoint load that hung up on feeding early on in the firing of this weapon. Accuracy was very good. I tested for accuracy at a distance of fifty yards, as this is a pistol-caliber carbine. Pictured are the smallest and largest groups fired.  Most ammunition grouped well under the one inch mark at fifty yards for five-shot groups fired from the bench. 

The point can be argued that a pistol-caliber carbine is very useful in some situations, and makes sense for a home defense weapon. A 9mm cartridge has much less recoil and muzzle blast than does the 5.56mm round when fired from a weapon of equal barrel length and weight. Muzzle blast can be a big concern when fired inside a building, and muzzle flash can also be very distracting in low light. The CMMG 9mm carbine offers low recoil, low muzzle blast, and low muzzle flash, compared to a 5.56mm carbine. It is much easier to learn to fire effectively for those who are bothered by recoil and noise. 

For those desiring a 9x19mm carbine, the CMMG MK-9 T is a very good choice. It is reliable, accurate, easy to fire, and made in the USA. MSRP as of the date of this review is $1149.95 US. Check out the entire line of CMMG rifles and accessories online at

Jeff Quinn

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Click pictures for a larger version.





Thirty-two round steel magazine.





Best & worst groups fired at 50 yards.