The CMMG Fixed Ejector Upper Group for BANSHEE Mk4, Mk9, Mk17 & MkGs platforms brings serious 9mm firepower to your AR in a compact, manageable package. This 8-inch upper harnesses CMMG's radial delayed blowback operating system—a refined evolution of the original platform that delivers reliable function without the complexity of traditional alternatives. If you're building or upgrading a 9mm AR that balances carbine-like ballistic performance with real-world portability, this upper group handles the heavy lifting for you.
What sets this upper apart is the complete package approach. You're not buying a bare receiver; CMMG includes a properly headspaced bolt carrier group, ZEROED polymer dust cover, ZEROED ambidextrous charging handle, and a ZEROED linear compensator—all tuned to the 9mm platform. The 8-inch barrel sports a 1:10 twist in a mid-profile contour, threaded 1/2 x 28 for the included muzzle device. The upper itself is billet 6061-T6 aluminum topped with CMMG's EML7 M-LOK handguard, finished in Armor Black Cerakote for durability and aesthetics. Weighing just 3.0 lbs over 16.5 inches, this upper works with CMMG 9mm conversion magazines and compatible lower receivers, making it a straightforward addition to existing builds.
Whether you're running this on a dedicated BANSHEE lower or pairing it with mil-spec lowers using CMMG's 9mm magazines, you get a shooter-friendly package that's ready to go. The fixed ejector system and delayed blowback design mean less noise, less blast, and more control—ideal for indoor ranges, home defense setups, or anyone who values a softer-shooting, easier-handling AR-pattern 9mm.
| Caliber | 9mm Luger |
| Barrel Length | 8 inches |
| Barrel Twist | 1:10 |
| Barrel Contour | Mid-Profile (MT) |
| Barrel Material | 4140CM SBN |
| Muzzle Thread | 1/2 x 28 |
| Muzzle Device | CMMG ZEROED Linear Compensator |
| Operating System | Fixed Ejector Radial Delayed Blowback |
| Upper Receiver | Billet 6061-T6 Aluminum |
| Handguard | CMMG EML7 M-LOK |
| Charging Handle | CMMG ZEROED Ambidextrous |
| Finish | Cerakote (Armor Black) |
| Weight | 3.0 lbs |
| Overall Length | 16.5 inches |
| Compatible Platforms | BANSHEE Mk4, Mk9, Mk17, MkGs |
This upper is designed for CMMG BANSHEE Mk4, Mk9, Mk17, and MkGs platforms. It also works with mil-spec AR15 lower receivers when paired with CMMG's 9mm conversion magazines.
You get the complete upper assembly with bolt carrier group, billet aluminum upper receiver, CMMG EML7 M-LOK handguard, ZEROED polymer dust cover, ZEROED ambidextrous charging handle, and ZEROED linear compensator—everything needed to mount on a compatible lower.
The fixed ejector design is integrated into CMMG's radial delayed blowback system to optimize reliability and function in the 9mm platform. This configuration reduces felt recoil and improves control compared to traditional direct impingement or straight blowback systems.
With its 8-inch barrel, this upper is compact and suitable for short-range applications, though the specific legal classification (SBR, pistol, or other) depends on your lower receiver choice and local regulations—always verify compliance before building.
CMMG
CMMG
