CMMG Banshee Mk4 Complete Upper Features The CMMG Banshee Mk4 Complete Upper is chambered in .338 ARC a cartridge designed to deliver more energy on target than .300 AAC Blackout while requiring less gas system tuning when switching between suppressed and unsuppressed shooting. Its 10.5 inch barrel uses a 1:8 twist rate a slower twist chosen specifically to stabilize the more traditional construction .338 caliber projectiles that handloaders prefer to work with. Because .338 ARC shares the same bolt as 6.5 Grendel AR-15 builds parts compatibility across these related platforms is maximized simplifying inventory for shooters running multiple calibers. The barrel is made from 4140CM steel with a nitride finish for corrosion resistance and long service life under repeated firing. A CMMG ZEROED Linear Compensator comes mounted to the barrel s 5/8x24 threads managing recoil and muzzle rise while keeping the overall package compact for pistol-length builds. The non-adjustable 0.750 inch gas block simplifies the operating system reducing points of failure in the Direct Impingement design. Topping the build is a billet 6061 T6 aluminum Mk4 upper receiver paired with an EML9 handguard giving shooters a rigid mounting platform for lights optics and other accessories. Finished in black and weighing 3.1 pounds this complete upper is a strong option for AR-15 builders looking to add large bore capability to their platform available for sale at GrabAGun. CMMG Banshee Mk4 Complete Upper Specifications Manufacturer: CMMG Model: Banshee Mk4 Complete Upper Caliber: .338 ARC Barrel Length: 10.5 Barrel Twist: 1:8 Barrel Material: 4140CM Nitride Finish Muzzle Device: CMMG ZEROED Linear Compensator Muzzle Thread: 5/8x24 Gas Block: Non-Adjustable 0.750 Upper Receiver: Mk4 Billet 6061 T6 Aluminum Handguard: EML9 Operating System: Direct Impingement Color: Black Weight: 3.1 lbs Available At: GrabAGun