The CMMG Mk4/AR15 Stripped Lower Receiver (brand part no. 55CA102MB) gives builders a forged 7075-T6 aluminum foundation for their next AR-15 build, finished in a distinctive Midnight Bronze anodized color instead of standard black. CMMG machines the Mk4 lower to Mil-Spec dimensions, so it’s compatible with the wide range of AR-15 and multi-caliber upper receivers and lower parts kits already on the market. Shipping as a stripped receiver, it’s ready for the buyer’s own choice of trigger, grip, and stock rather than locking builders into a pre-selected parts kit. Among rifle lowers, this CMMG Mk4 suits builders who want a proven name-brand receiver in a finish that stands out from the crowd.

Key Specifications

• Machined from forged 7075-T6 aluminum.
• Finished in Midnight Bronze anodized color.
• Cut to Mil-Spec dimensions, compatible with standard AR-15 lower parts kits.
• Compatible with multi-caliber AR-15 platform builds.
• Sold as a stripped receiver, ready for the buyer’s own parts kit.

Frequently Asked Questions

Does this receiver come with a trigger or parts kit installed? No, it ships as a stripped receiver — you’ll need to add a compatible AR-15 lower parts kit, trigger, and stock separately.

Will it work with any AR-15 upper? Yes, it’s machined to Mil-Spec dimensions, so it’s compatible with standard AR-15 and multi-caliber upper receivers.

Buy the CMMG Mk4/AR15 Lower Receiver

A forged 7075-T6 lower in a distinctive Midnight Bronze finish gives your next AR-15 build genuine CMMG quality with standout style. As a firearm, it ships to your FFL — order from our Lubbock, Texas gun shop and we’ll get the transfer started as soon as it’s ready to ship.