Last week, CMMG reintroduced their popular Mk9 with a new radial delay blowback system. The Mk9 series is one of the most popular straight blowback pistol caliber carbines (PCCs) offered by CMMG. The updated Mk9 receives a brand new operating system and now takes Colt Commando magazines.

The new Mk9 will be a great addition to the CMMG extensive PCC lineup. The new Mk9 features a reduction in felt recoil due to the Radial Blowback System allowing smoother cycling. Along with inclusion of the durable, rugged, and reliable Colt mags creates a formidable combination for consumers. The modernization process of the Mk9 will be available in the Banshee and Resolute in all barrel lengths including their 16’ inch variants. The difference between the series offers more premium features from the factory based on what you are willing to splurge.

Below is CMMG’s press release on the updated Mk9.

Press Release

The Mk9 has been a staple in CMMG’s line-up for years. Featuring a dedicated magwell designed to accept Colt SMG-style 9mm magazines, the Mk9 has always been one of CMMG’s most popular firearms.

Up until recently, the Mk9 utilized a straight blowback operating system, similar to most 9mm AR’s on the market.

CMMG has now upgraded the Mk9 to utilize the patented Radial Delayed Blowback™ operating system, available in BANSHEE™ and RESOLUTE configurations. Offering significantly less felt-recoil, Radial Delayed Blowback has proven to be superior to the old straight blowback design and this change completes CMMG’s transition to the new and better operating system.

The Mk9 BANSHEE is offered as a pistol or short barreled rifle with barrel lengths of 5 or 8 inches in length, while Mk9 RESOLUTE rifles come with a 16-inch barrel. Both the BANSHEE and RESOLUTE offer Last Round Bolt Hold Open.


Along with offering complete Mk9 firearms and lower receiver groups that are designed to utilize Radial Delayed Blowback, CMMG offers Mk9 Upgrade Kits for those who already have an older CMMG Mk9 Lower Receiver.

The Mk9 Upgrade Kits have all the parts needed to make an old Mk9 compatible with a CMMG 9mm Radial Delayed Blowback upper receiver, including a mag catch, bolt catch, carbine buffer assembly, carbine action spring and feed ramp.

It’s important to note that there are two different versions of the Mk9 Upgrade Kits. Depending on the types of magazines you plan to use, you will want to either select the ASC/CPD magazine version or the Colt/Metalform magazine version. The kit you select will include a feed ramp that is designed for optimal reliability with that style of magazine. If you have any questions on which Mk9 Upgrade Kit is right for you, please email


If you’re planning to purchase a Mk9 lower receiver group or if you are planning to upgrade your existing Mk9, it is important that you check whether your CMMG 9mm Upper Receiver will be compatible.

CMMG has made a small modification to its 9mm barrels in order for them to be compatible with Mk9 lower receivers. This modification only applies to Mk9 platform lower receivers and does not positively or negatively affect functionality of the barrel with a MkGs, Mk4 or Mk17 platform lower receiver.

Barrels that are stamped “9mm Luger” will be compatible with an upgraded Mk9 lower receiver. If your barrel is marked “9×19 NATO”, you will need to purchase a new 9mm barrel in order to ensure reliable function.

Not sure of the new price point of the updated Mk9. I hypothesize that it will be comparable to the 9mm Banshee PCCs sold by CMMG. To find out more you can visit, for more.

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