CMMG Banshee Mk4 .338 ARC 10.5" Upper Receiver
CMMG's Banshee Mk4 upper receiver in .338 ARC delivers large-bore stopping power with AR-15 platform compatibility. Features a 10.5" nitride barrel, direct impingement system, and linear compensator.
Fits: AR-15
The .338 ARC Advantage
The CMMG Banshee Mk4 upper receiver represents a thoughtful evolution of the AR-15 platform. By chambering the .338 ARC cartridge, this upper combines the familiar ergonomics and modularity of the AR-15 with the terminal performance of a larger caliber.
Design and Compatibility
The .338 ARC was engineered to deliver what 300 Blackout promises: effective performance whether suppressed or unsuppressed, but with more energy downrange and fewer gas system compromises. The cartridge uses the same bolt as 6.5 Grendel AR-15s, ensuring straightforward parts compatibility for those building or upgrading existing rifles.
Barrel Specifications
This upper features a 10.5" barrel with a 1:8 twist rate—a deliberate choice that accommodates traditional .338 caliber bullet construction. Shooters who reload will appreciate this flexibility. The barrel is constructed from 4140 chromium-molybdenum steel with a durable nitride finish.
Integrated Components
- Upper Receiver: Billet 6061-T6 aluminum with Cerakote finish
- Handguard: EML9 design for ergonomic control
- Gas System: Compact action direct impingement with non-adjustable 0.750" gas block
- Charging Handle: Dissent side charger for ambidextrous operation
- Muzzle Device: CMMG ZEROED linear compensator (5/8 x 24 threads)
- Weight: 3.1 lbs
Practical Performance
This is a complete upper receiver group—everything you need to pair with a compatible lower receiver. The compact 10.5" barrel makes this upper suitable for short-range work, home defense, or suppressed applications where maneuverability matters.
