Unique aesthetic with CMMG MkG 45 Guard is 15-inch KeyMod Rail surrounding 16-inch barrel with SV brake protruding from forend. End user can modify rifle as needed. Photo: CMMG

The urge to take advantage of AR modularity, ergonomics, optics mounting, and accuracy with cartridges other than 5.56mm has constantly appealed to the shooting community.CMMG has experience with this in the form of their highly successful Mk47 Mutant 7.62x39mm, Mk9 9mm, and MkW ANVIL .458 SOCOM rifles. CMMG has taken this a step further with their new MkG Guard in .45 ACP.

The MkG is not merely a modified/upscaled 9mm AR-pattern weapon chambered in .45 ACP using the customary blowback operating method. CMMG has designed a patent-pending Radial Delayed Blowback (RDB) operating system. The advantages are numerous for both manufacturer and, more importantly, the user.

Many will turn to CMMG MkG Guard for reduced recoil and muzzle blast represented by .45 ACP pistol cartridge in lieu of the increasingly popular short-barreled rifles chambered in 5.56, 6.8 SPC, or 7.62×51.

CMMG is able to reduce manufacturing cost by using similar tooling, methods, parts, and techniques familiar to the AR-15 versus the hunk of metal typical in the previous blowback AR SMG models. The user is rewarded with a .45 ACP AR rifle that is not only lighter overall, but also offers milder recoil during use.A heavy bolt mass is no longer needed to control pressures as in a strictly blowback operating method. The CMMG RDB rotates and unlocks (like the AR-15) before cycling to the rear versus just moving rearward upon the round being fired, thus slowing the bolt carrier group enough to let the pressure drop, allowing for safe functioning.

Even though .45 ACP is the CMMG MkG’s chambering, the bolt carrier and buffer are lighter than a 9mm AR using standard blowback method. This translates into less recoil and a more controllable rifle in rapid fire, since the pound or more mass of metal is no longer recoiling rearward then slamming forward again.


CMMG designed Guard’s lower to accommodate Glock 21-style magazines, including oversized magazine release button.

The CMMG MkG Guard tested was the DRB2 model featuring a Magpul MOE pistol grip and CTR adjustable length stock. The 16.1-inch 4140 medium taper barrel and 7075-T6 billet lower and forged upper contributed to a weight of 5.8 pounds. The Guard is 32.5 inches long with stock collapsed.CMMG wisely decided to utilize Glock 21 (G21) magazines with the MkG and not some proprietary feeding device. Glock magazines are known for their reliability and are abundant and reasonably priced.

Will the Kriss USA 25-round modified G21 magazines work with the MkG? I cover this in more detail later, but the short answer is yes.

The CMMG MkG Guard accommodates the G21 magazines with a patent-pending bolt catch linkage that locks the bolt rearward after the last round and is released simply by pushing an oversized release button. More attention to detail is found with the integrated oversized trigger guard and a flared magazine well machined into the billet 7075 aluminum lower.

The MkG Guard evaluated herein is a rifle version with 16-inch barrel. Other model configurations are available, including pistol, pistol with brace, and SBR. Every CMMG Guard comes threaded in the popular .578-28 .45-caliber suppressor pattern. The .45 ACP carbine is the perfect candidate for suppressor use, considering the .45 ACP is subsonic in most ammunition offerings.

CMMG offers optional Action Tuning Kit for MkG Guard. User can adjust action for light loads, hot loads, or suppressor use via simple method of adding weight to bolt carrier.

CMMG offers an optional Action Tuning Kit for the MkG Guard that lets you adjust the action for light loads, hot loads, or suppressor use via a simple method of adding weight to the bolt carrier.


Many will question the utility of employing a pistol cartridge in a shoulder-fired weapon. Why not just use a rifle round? Some would argue that most engagements happen well within a 100-yard range, especially in a civilian setting, and that handling and reliability are more important factors in quick, reactive engagements than the specific caliber used.

CMMG RDB rotates and unlocks (like the AR-15) before cycling to the rear versus just moving rearward upon round being fired. This slows bolt carrier group enough to let pressure drop, allowing for safe functioning.

Less experienced shooters will also find the lower recoil pulse, especially with the CMMG MkG, and muzzle blast of a pistol caliber fired from the shoulder easier to manage, which often translates into better accuracy potential.Will a rifle hit with more authority than a .45 ACP? Absolutely! But do not underestimate the advantages of carrying a handgun and carbine using the same easy to acquire and relatively inexpensive ammunition.

Not to delve into worst-case scenarios, but too many people are stocking ammunition, food, and weapons in these times of worry to totally discount the sentiment.

The concept is taken a step further with the CMMG MkG’s utilization of Glock 21 magazines. Ideal companion handguns for use with the MkG Guard .45 ACP are the Glock 21 or 41. What could be better than not only using the same cartridge but also the same magazines?

Kriss extended 25-round magazines were ideal for use with CMMG Guard.

Further along these lines of dual-use magazine is the Kriss G25 MagEx kit. The MagEx is a 12-round extension for the standard G21 13-round magazine, bumping up the capacity. This is especially useful when using a pistol-chambered carbine like the CMMG MkG.The magazine extension has inner and outer sleeves of composite material and requires no special tools to convert a standard G21 magazine to 25-round capacity.


High Threat Concealment’s (HTC) LPS (Low Profile System) belt rig was used to combine the CMMG MkG and Glock handgun during range T&E. The LPS is an adaptation of the patrol belt concept that can be concealed under a light jacket or over shirt.

According to HTC literature, the LPS is tailored to those assigned to dignitary/executive protection details or for any personnel operating in a non- or semi-permissive high-threat environment. HTC utilizes the latest in compression molding, vacuum forming, and injection molding combined with the highest quality thermoplastics and milspec hardware to make some of the most effective low-profile tactical gear available today.

All HTC products and accessories are proudly manufactured in the USA.

Many will turn to the .45 ACP CMMG MkG for the reduced recoil and muzzle blast represented by the .45 ACP pistol cartridge in lieu of the increasingly popular short-barreled rifles chambered in 5.56mm, 6.8 SPC, or 7.62x51mm. Others point to it for the ease of suppressing the .45 ACP.


Thanks to CMMG’s design, Guard’s ability to lock bolt to the rear after last round is fired is an improvement over 9mm ARs.

A SIG Sauer SRD45 suppressor was used with the MkG. Range time consisted of not only testing accuracy and reliability of the CMMG Guard with all types of ammunition, but also ensuring that the suppressor in no way compromised the established baselines of accuracy and reliability once the proper tuning kit was installed.A pleasant surprise was the consistent point of aim enjoyed no matter the weight or type of .45 ACP load used. The 230-grain .45 ACP is generally subsonic and the obvious choice for use with a suppressor. The SIG suppressor proved effective at taming the muzzle blast of even the supersonic 185-grain .45 ACP loads. With the SIG suppressor installed, all loads could be comfortably fired without ear protection.

I used an assortment of premium self-defense JHP and FMJ ammunition while evaluating the CMMG MkG Guard: Black Hills 230-grain JHP, Federal Premium 230-grain HydraShok, Hornady TAP-FPD 230-grain, SIG Sauer 230-grain FMJ and JHP, and Winchester 230-grain FMJ.

CMMG Guard with Trijicon ACOG produced excellent accuracy at 50 yards firing from improvised field rests.

A Trijicon 3.5X TA33H ACOG was mounted to support the T&E. My initial thought was to use the ACOG and then mount a Trijicon RMR Type 2, but the ACOG fit the rifle so well I left it in place for the duration.Firing was at a relatively steady pace, with different shooters running the MkG on plate racks, dueling trees, and in other drills.

The CMMG Guard had no issue digesting JHP profile bullets. This is an important issue, as law enforcement agencies and private citizens use expanding ammunition to limit overpenetration in CQB situations, not to mention its increased terminal effectiveness.


Premium ammunition from Black Hills, Federal, Hornady, and SIG was used with CMMG Guard.

Drills around barricades and moving through doorways had the CMMG MkG showing its merit. After all, the MkG is a six-pound AR-pattern weapon which is known for excellent ergonomics and handling.Numerous range evaluators, myself included, were struck by how easy it was to shoot while moving with the CMMG MkG Guard. This is surely a result of CMMG’s Radial Delayed Blowback operating system managing recoil as designed.

For comparison’s sake, I brought a 9mm AR to one of the range sessions. CMMG’s claims about lighter felt recoil and being able to control the MkG in .45 ACP better during rapid strings of fire were borne out.

The CMMG MkG Guard proved accurate and durable during testing at Echo Valley Training Center, with nearly 400 rounds fired over several range visits. The Guard delivers on its promises of reduced recoil and muzzle climb, making a user more effective in engaging targets rapidly.

The ability of the MkG Guard to interact so well with the Glock chambered .45 ACP handguns has to be viewed favorably, with so many departments already issuing their personnel G21 or G41 handguns. This will no doubt also influence private citizens to consider it a viable option to combine the CMMG MkG and Glock pistols.

The inherent familiarity most have with the AR platform, not to mention its ergonomics, validates CMMG’s decision to continue to enhance it via caliber expansion. There are many situations in which the penetration and power of a 230-grain .45 bullet fired from an AR-type weapon could be very advantageous.

In designing and building the MkG Guard, CMMG has taken a proven weapons system and made it better. The CMMG MkG Guard places real power in a compact, accurate, and reliable package. The ability to reliably engage targets out to 100 yards with great terminal effect cannot be underestimated.


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