CMMG’s Delayed Blowback System Open Door for Large Pistol Caliber ARs

The concept isn’t new, but it has never been applied to ARs before.

CMMG invented the Radial Delayed Blowback system
CMMG invented the Radial Delayed Blowback system—the concept isn't new, but it has never been incorporated into an AR design before.CMMG

About five years ago, when all of its competitors were scrambling to feed the craze of AR9 PCC (pistol caliber carbine) switching over to Glock magazines, CMMG started looking for a way to stand out from the pack by providing consumers with a .45 ACP PCC option. Initially, product designers tried doing things the traditional way, but when they met with failure after failure, they decided to look at the problem differently and try something a little more radical. What they came up with not only provided them with a new patented technology, but also opened the door for a host of new choices for shooters who are looking for large-caliber PCC options.

When CMMG first started developing a .45 ACP option, it built the model using the straight blowback design used with the 9mm PCC. It didn’t take them long to realize that the .45 ACP rounds created some issues with the system.

“We figured out that the recoil was so harsh that rounds were jumping out of the magazine,” says Jordan Wilson, CMMG product design manager. “Once we realized that was going on, we knew the straight blowback wouldn’t work.”

CMMG went back to the drawing board.

“We tried a gas-powered direct-impingement system, but it had the exact opposite problem as straight blowback, and we realized it wasn’t going to work either,” Wilson says.

With the traditional systems exhausted, CMMG started looking for something new. What they came up with was the Radial Delayed Blowback system.

The delayed blowback system wasn’t new, but it had never been incorporated in an AR platform before. Once again, the designers at CMMG met with failure after failure. They seemed to realize the potential in the system they were testing, however, and continued modifying the design to overcome the flaws of the previous model. And then, finally, the perseverance paid off, and the idea became reality.

The Radial Delayed Blowback system that CMMG developed not only solved the problem of rounds jumping out of the magazine, it also created several distinct advantages to the design.

“Where this system really shines is that it has significantly lighter weight so you get substantially less felt recoil, which allows for quicker follow-up shots,” Wilson says. “And because we’re forcing more of that gas out of the barrel, you’re also getting more velocity and better performance when you’re using a suppressor.”

Arguably the biggest benefit of the system, however, is the door it opened for other large pistol calibers. Since CMMG first launched the system for .45 ACP, they have successfully adapted it to accommodate four other calibers. And with the patent CMMG just received for the technology, it’s safe to assume more calibers will be coming soon. Booth #15942. (

Editor’s Note: this article is a corrected version of the article that ran in SHOT Daily on January 24, 2020.