CMMG AR-15 Banshee 100 Mk4 .22LR 4.5" Pistol Upper Receiver Assembly with M-LOK Handguard

The CMMG AR-15 Banshee 100 Mk4 .22LR upper receiver assembly brings fun, low-recoil shooting to the AR platform without compromise. This complete upper pairs CMMG's proven Mk4 design with a short 4.5" barrel—the shortest .22LR option CMMG offers—making it an ideal choice for shooters who want a compact, maneuverable .22 build that works with any standard AR-15 lower receiver. Whether you're zeroing new shooters, practicing at reduced cost, or just enjoying tack-driving accuracy in a familiar platform, this upper delivers the precision and modularity the AR ecosystem is known for.

Built on a billet 6061-T6 aluminum receiver, the Banshee 100 upper uses CMMG's traditional blowback operating system optimized for .22LR reliability. The barrel—4140CM steel with a 1:16 twist and MT contour—threads 1/2×28 and wears a CMMG ZEROED flash hider. The M-LOK handguard provides modern accessory mounting without bulk, keeping the upper lean at just 2.2 pounds and 12.8 inches long. This is a pistol-length upper, so it pairs naturally with pistol-sized lowers for compact configurations.

You're getting a complete, ready-to-function assembly here. Every upper includes the bolt carrier group, ZEROED polymer dust cover, ZEROED ambidextrous charging handle, and ZEROED flash hider already fitted and zeroed. Just mate it to your lower, load .22 AR conversion magazines, and shoot. The Mk4 platform and standard AR controls mean no learning curve. Choose from six Cerakote finish options to match your rig or build aesthetic.

Key Features

• 4.5" barrel—shortest .22LR option from CMMG—for compact, quick-handling profiles
• Mk4 platform compatible with any standard AR-15 lower receiver
• Complete upper assembly: bolt carrier group, charging handle, flash hider, and dust cover all included and zeroed
• Billet 6061-T6 aluminum receiver for precision and durability
• M-LOK handguard with modern accessory mounting
• Traditional blowback operation tuned for .22LR
• Six Cerakote finish options
• Lightweight at 2.2 lbs; compact at 12.8" overall length

Specifications

Frequently Asked Questions

What lower receiver does this .22LR upper work with?

The Banshee 100 Mk4 upper is designed to work with any standard AR-15 lower receiver. You'll need to use CMMG .22 AR conversion magazines with it.

Is this upper fully assembled and ready to use?

Yes. The upper comes complete with the bolt carrier group, dust cover, charging handle, and flash hider. It arrives zeroed and ready to attach to a lower receiver.

How short is this upper compared to other .22LR barrels?

At 4.5", this is the shortest .22LR barrel option CMMG currently offers in any caliber, making it ideal for compact builds.

Can I change the handguard or other components?

The upper ships with CMMG's EML4 M-LOK handguard. The platform is Mk4, so verify compatibility if you plan to swap any components.