CMMG Resolute MkGs: A Serious PCC

The CMMG Resolute MKGs Rifle is accurate, rugged and fun to shoot.

CMMG Resolute MkGs: A Serious PCC

It used to be that an AR-style carbine chambered in a pistol caliber like 9mm Luger was a special gun used only by law enforcement or the military. Then some people discovered it was much less expensive to shoot than an AR chambered in .223 Remington. And while that hasn’t changed, more and more people have found that an AR chambered in 9mm Luger is great for fun, competition and even self-defense.

CMMG was founded in 2002 and has designed its own AR-style pistol caliber carbine. This is not a toy or hobby carbine. It’s a serious gun, and with the improvement in recent years in 9mm projectiles, is a formidable self-defense gun. Not only are bullets better at stopping threats, but there is a bit of an increase in bullet velocity from a 16-inch barrel compared to a handgun. This obviously helps deliver more energy to the target. A 10mm version is also available.


The CMMG Resolute MkGs Rifle has a shorter barrel than the common AR-style rifle, so it could be called a carbine. And more importantly, the action is a bit different than a standard AR. Instead of a direct gas impingement (DGI) system that is common on the standard AR-15 or M16, it has a CMMG-designed delayed blowback action. This is not the more common blowback action where the bolt is held closed by inertia long enough for the bullet to exit the barrel, allowing gas pressure to drop to a safe level for the breech to be opened.

Instead, although recoil does operate the bolt, the bolt is locked to the barrel by lugs the same way the bolt is locked in a traditional DGI gun. Then when recoil starts to send the bolt carrier assembly to the rear to cycle the gun, the bolt first rotates and unlocks from the lugs in the barrel extension. That causes a slight delay, allowing the bullet to exit the barrel and gas pressure to drop before the bolt is sent to the rear.

CMMG says the system results in a slight decrease in felt recoil but that’s nearly impossible to measure without testing an identical blowback-action gun with the same weight against the delayed blowback design. Complicating the test would be the fact that everyone feels recoil differently. What is heavy recoil to one person may be mild to another. In testing, for me at least, that recoil was mild and not punishing. And I don’t particularly like recoil.

The company recommends against using cast, wadcutter or semi-wadcutter bullets in the carbine because it’s likely that those bullet designs will not function well. But CMMG, unlike most other manufacturers, does not tell owners to use only factory ammunition. Restricting use to only factory ammunition is fairly common today, and although CMMG does not say the owner should never use it, the company does caution that some reloaded ammunition may not function correctly in the gun, and that any warranty claims using reloaded ammunition are subject to special review. That seems reasonable considering there are no tests or quality control measures used by the typical handloader. And some handloaders just aren’t as careful as others.

Construction and Function

The Resolute is built to function with Glock 9mm magazines. They are everywhere and generally pretty reliable, so that’s a good choice. For testing, I used a 15-round and a couple 33-round magazines. The gun was reliable with all of them. But according to CMMG, Gen2 or older Glock magazines might not work and need modification to be suitable, so it’s best to stick with Gen3 or Gen4 magazines. Most gun shops carry them, so as a retailer, it’s probably not going to be necessary to stock a whole new line of magazines to accommodate your customers.

Because the gun is based on the AR-15, many parts are interchangeable with standard AR-15 parts. You may need to contact the factory to find out if a part you have in mind will work with the Resolute, but some will. For example, any GI-style AR-15 charging handle should work. Any GI-style pistol grip should also work. These are particularly important items, especially if the owner plans to practice with the Resolute instead of a .223 Remington to save ammunition costs. In that case, it would be a good idea for both the practice and carry guns to be configured the same way and have the same feel.

You should caution your customers to be careful if they’re considering replacing Resolute parts with standard AR-15 parts. At first glance, a part may look the same, but it may not be. An example is that although the bolt and bolt carrier look very similar to those of a standard AR-15 DGI gun, the gas key has no hole in it, so it doesn’t carry any gas. But it is staked correctly, and that’s a nice touch.

Additionally, the bolt is very similar to a standard bolt, but there is a spring surrounding the tail to push the bolt into battery. That makes it different. The bolt is made of 9310 AMS6260 steel and the upper and lower receivers are made of 7075 T6 aluminum. The M-Lok compatible handguard, which has a Picatinny rail along the top, is manufactured from 6061 T6 aluminum and the gun barrel is made of 4140 chrome-moly steel that is finished in a salt nitride bath making it extremely corrosion and wear resistant.

And CMMG doesn’t rely on a spacer block to reduce the size of the standard AR-15 magazine well to accommodate the smaller 9mm magazine. Instead, CMMG manufactures a lower receiver with the proper-size magazine well. Also, CMMG has designed a special bolt hold-open system that is patented and that works well in holding the bolt open after the last round in the magazine is fired.

The lower receiver extension, also called the buffer tube by some, is of the standard military diameter so any buttstock that is suitable for an AR with that size extension will work with the Resolute. This is another area where the owner can customize the gun to suit their desires. Accessories like that, as well as charging handles and grips that are mentioned above, can be additional sources of revenue for the gun shop so they should not be overlooked. The buffer tube is easy to remove and replace because the retaining nut, or the castle nut as some call it, is not staked and isn’t tightened with thread locker. This means it should be fairly easy to remove and replace the buffer tube. That may be good or bad depending on your viewpoint. But if the owner is worried that the nut could come loose, it would be easy to stake.

While the 9mm carbine worked fine with the factory buffer, CMMG cautions that in its 10mm model, the user may need to change the buffer for reliable function due to the wide power level variation in different 10mm ammunition.

The CMMG Resolute carbine carries a lifetime warranty but requires an invoice or proof of purchase when submitting the gun for service. So, caution your buyer to hold onto the receipt — just in case.

On the Range

The Resolute was a lot of fun to shoot. I tested it in self-defense drills using both a SIG ROMEO4 red-dot sight and an EOTech 1-6x24mm Precision Rifle Scope mounted on a GG&G QD FLT Mount. Recoil was very manageable and when shooting off a bench for accuracy at 50 yards, the gun was surprisingly precise. In fact, it was a lot more accurate than a gun of this type needs to be. The best group was .41 inch with Hornady 135-grain Critical Duty ammunition. It’s a 9mm carbine, so 50 yards is the customary test range, but that group size is less than one minute of angle. That’s precision rifle results in a pistol caliber carbine. If accuracy is that important to your buyer, this gun is capable of delivering.

Although the gun does not come with sights, it is easy to mount them. Besides, many buyers change factory sights because they don’t like the choice of the manufacturer. So why pay for a set that will be discarded? Not including them helps to keep the cost of the gun down.

There is no question that with an MSRP of $1,300, this is not a cheap pistol-caliber carbine. But it’s not meant to be. This is not a hobby gun. It’s a gun that is designed for serious work and that can be used for extended heavy-duty practice.


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