CMMG Banshee 100 Mk4 AR-15 Pistol Upper Receiver Assembly, 4.6x30mm, 8" Barrel, M-LOK Handguard

The CMMG Banshee 100 Mk4 AR-15 pistol upper receiver assembly brings the 4.6x30mm cartridge—a caliber purpose-built for short-range precision and light recoil—into a platform that works with your standard AR-15 lower. This is a complete upper assembly ready to run out of the box: it includes the bolt carrier group, charging handle, dust cover, and muzzle device all zeroed and functional. Pair it with any mil-spec AR-15 lower receiver and CMMG 4.6x30mm magazines, and you've got a compact, flat-shooting PDW (personal defense weapon) that handles like nothing else in the rifle world.

Built around an 8-inch 4140CM SBN barrel with a 1:5.9 twist and micro gas port, the Banshee 100 runs direct impingement through a FourSix-specific .750 gas block optimized for the cartridge's ballistics. The billet 6061 T6 aluminum upper and M-LOK handguard give you a lightweight, rigid platform for accessories and confident handling. At 3.2 pounds and 16.5 inches overall length, this upper transforms into a genuinely packable firearm—ideal for truck duty, home defense drills, or anyone who wants a seriously soft-shooting AR platform without the footprint of a full rifle.

CMMG has engineered every detail for the 4.6x30mm round: the linear compensator tames what little recoil exists, the ambi charging handle works either shoulder, and the whole assembly arrives cerakoted and ready to work. This is the thinking shooter's upper—less blast, less recoil, more control, and a cartridge designed from the ground up to do what it does exceptionally well.

Key Features

• Complete upper receiver assembly—includes bolt carrier group, charging handle, dust cover, and muzzle device
• 8-inch 4140CM SBN barrel optimized for 4.6x30mm ballistics
• Direct impingement system with FourSix-specific gas block and micro gas port
• Billet 6061 T6 aluminum upper receiver for strength and rigidity
• CMMG EML7 M-LOK handguard for modularity and accessory mounting
• CMMG ZEROED Linear Compensator (1/2 x 28 threads) pre-installed
• Ambi charging handle for either-hand operation
• Compatible with standard AR-15 lower receivers and CMMG 4.6x30mm magazines
• Factory cerakoted finish
• Lightweight design at 3.2 lbs for compact, maneuverable handling

Specifications

Frequently Asked Questions

What AR-15 lower receiver does this upper work with?

The Banshee 100 Mk4 upper is designed to work with any standard AR-15 lower receiver. You'll also need CMMG 4.6x30mm magazines to feed the cartridge.

What comes in the box with this upper assembly?

The upper assembly ships complete and zeroed, including the bolt carrier group, dust cover, ambi charging handle, and linear compensator. Everything is ready to mount on a lower and shoot.

What is the 4.6x30mm cartridge, and why use it?

The 4.6x30mm is a purpose-built PDW cartridge engineered for soft recoil, flat trajectory, and precision at close to intermediate range. CMMG pioneered civilian access to this round in the U.S., and the Banshee 100 is purpose-optimized for it—lighter recoil than 5.56 NATO, superior control, and a compact package ideal for defensive use and training.

Is this upper suitable for hunting or home defense?

The 4.6x30mm and 8-inch barrel are designed for personal defense and short-range work. Check your local laws and your specific use case before selecting any firearm or cartridge for hunting or defense.