CMMG BANSHEE MK4 5.56x45 10.5" Upper Group - Black

The CMMG BANSHEE MK4 5.56x45 10.5" upper group is purpose-built for shooters who prioritize compact size and lightweight handling without sacrificing reliability. At just 10.5 inches, this is CMMG's shortest 5.56mm upper offering—ideal for those building an ultra-compact AR15 that moves fast in tight quarters, fits easily in a vehicle, or simply feels right in your hands. Whether you're assembling a truck gun, a home-defense carbine, or a nimble range build, this upper delivers the firepower of 5.56 in a footprint that goes places bigger rifles can't.

Everything arrives ready to run: the upper comes complete with bolt carrier group, polymer dust cover, ambidextrous charging handle, and CMMG's ZEROED linear compensator. The billet 6061-T6 aluminum upper receiver pairs with an EML9 M-LOK handguard, giving you modern mounting flexibility without excessive weight. The 4140CM barrel features a 1:7 twist and carbine-length gas port, tuned for reliable operation in a short, direct-impingement system with a fixed 0.750" non-adjustable gas block.

At 3.5 pounds and 18.8 inches overall, the BANSHEE MK4 upper prioritizes portability and balance. The muzzle threads at 1/2x28 accept standard suppressors or brakes, and the linear compensator included here helps tame recoil and noise in close-quarters scenarios. The Mk4 platform is a proven CMMG design that keeps the short-barrel concept simple and functional—no exotic systems, just clean engineering that hunters, shooters, and outdoor enthusiasts have relied on.

This is a versatile upper for builders and tinkerers who want precision parts without the guesswork. Pair it with your favorite lower, zero in, and you've got a rifle that handles like a pistol but delivers rifle performance.

Key Features

• 10.5" barrel—CMMG's shortest 5.56mm upper for ultra-compact builds
• Complete upper group includes bolt carrier group and charging handle; ready to assemble
• Billet 6061-T6 aluminum upper receiver with integrated Picatinny rail
• EML9 M-LOK handguard for modular accessory mounting
• CMMG ZEROED ambidextrous charging handle for lefty and righty shooters
• CMMG ZEROED linear compensator (1/2x28 thread) included
• Polymer dust cover included
• Direct impingement operation with carbine-length gas port
• 1:7 barrel twist suited for standard and heavier 5.56 rounds
• 4140CM barrel material for durability
• Lightweight at 3.5 lbs with 18.8" overall length
• Cerakote finish for corrosion resistance

Specifications

Frequently Asked Questions

What lower receiver is this compatible with?

The CMMG BANSHEE MK4 upper is built on CMMG's Mk4 AR15 platform and will mate with any standard AR15 lower receiver that accepts a Mk4 upper.

Does this come ready to shoot, or do I need additional parts?

This is an upper group assembly, so you'll need to pair it with an AR15 lower receiver to complete a functional rifle. The upper includes the bolt carrier group, so assembly is straightforward once you have a lower.

What's included in the box?

The upper group comes complete with bolt carrier group, ZEROED ambidextrous charging handle, ZEROED polymer dust cover, and ZEROED linear compensator for the muzzle.

Is a 10.5" barrel legal to shoot on a rifle?

Short-barrel legality depends on your location and whether you're building a rifle or pistol. Consult your local and federal firearms laws before assembly. Many shooters use short barrels on AR pistols or registered short-barrel rifles (SBRs). This product is a component—final legality is your responsibility.

Can I suppress this with the included compensator?

The muzzle threads at 1/2x28 and the linear compensator included can be swapped for a suppressor of the same thread pitch. Check your suppressor specifications for compatibility with 5.56 rifles.