Since the inception of CMMG®’s Radial Delayed Blowback operating system, pistol calibers have never been more at home in the AR platform, free from the needs of a finicky gas system or heavy bolts and action springs to hold a traditional blowback action closed. Work with something long enough and eventually you figure out ways to do things differently, and Radial Delayed Blowback has not been immune to continued innovation.
During the development of the DISSENT and the Compact Action operating system, our engineers continued to evolve Radial Delayed Blowback with the use of a fixed ejector located in the upper receiver of the DISSENT, and it was only a matter of time before that evolution made its way into the already existing BANSHEE and RESOLUTE platform. That time is now!
All our BANSHEE and RESOLUTE firearms and upper groups that are chambered in 9mm and .45 ACP are now available with the same fixed ejector Radial Delayed Blowback action and operating system.
While the original Radial Delayed Blowback was designed to operate in a mil-spec style upper receiver, there wasn't a good way to integrate anything besides a DI style spring-loaded BCG ejector. Following the research and design of the DISSENT and its Compact Action, our engineers realized that with the advancements made in our Radial Delayed Blowback system and the freedom of not using mil-spec style uppers, a dedicated PCC upper with fixed ejector would be possible with the always popular BANSHEE and RESOLUTE.
One of the most obvious differences between the standard and fixed ejector Radial Delayed Blowback firearms is the size of the ejection port and dust cover. Since the fixed ejector model is dedicated to pistol calibers a smaller PCC size port is used, just like on the DISSENT firearms.
Top: Original ejection port.
Bottom: Fixed ejector Radial Delayed Blowback ejection port.
On the left hand side you will notice the the fixed ejector plate on the upper receiver.
From the inside you can see the fixed ejector itself and the bolt carrier group has a machined slot to match, allowing the BCG to travel independently of the ejector.
Short answer: all of the same ones the non-fixed ejector uppers are compatible with.
Long answer: 9mm FE uppers are compatible with all existing Mk4/AR15, MkGs, Mk17, and Mk9 lower receivers. (Mk9 lowers are compatible as long as they are the newer Radial Delayed Blowback lower WITHOUT the ejector built into the lower.)
.45 ACP FE uppers are compatible with MkG lower groups, same as the non-fixed ejector models.
Radial Delayed Blowback calibers like 5.7x28mm, 10mm, and 40 S&W don't have a fixed ejector version simply because there is little benefit to them. The direct impingement style BCG ejector that's been used for Radial Delayed Blowback since it's original introduction has proven itself to be optimal for these calibers.
For certain use cases, maybe. But for the overwhelming majority of people there isn't much difference. The Action Tuning Kit for the original Radial Delayed Blowback BCGs provides a wide range of tuning capability and has been go to for builders wanting to use mil-spec parts and receivers.
With such a wide range of 9mm and .45 ACP ammo loadings, the fixed ejector variants take full advantage of the ammo and manufacturing technology that didn't exist years ago.
The fixed ejector BANSHEES and RESOLUTES along with the original BCG ejector versions can be found on our website and at many dealers and distributors.