The CMMG Collapsible Stock Kit for AR-15 (brand part number 55CA634) bundles everything needed to finish out a mil-spec lower build in one box. CMMG built this kit around a 6-position receiver extension, matching carbine buffer assembly, carbine action spring, and a 6-position collapsible butt stock, so builders are not left hunting down individually compatible parts. The polymer-and-aluminum stock wears a black matte finish that matches most mil-spec AR builds, and every component is sized to mil-spec buffer tube diameter for broad lower-receiver compatibility. This is the kit to reach for when finishing a home-build lower or replacing a worn-out stock assembly without piecing components together from multiple vendors.

Key Specifications

• Kit includes a CMMG 6-position receiver extension sized to mil-spec buffer tube diameter for broad AR-15 lower compatibility.
• A matching carbine buffer assembly is included so the cycling weight is correctly matched to the stock and tube.
• The kit ships with a carbine action spring, completing the buffer system without needing a separate purchase.
• Includes a 6-position collapsible butt stock assembly for adjustable length of pull.
• Finished in black matte for a clean, mil-spec appearance that matches most AR builds.
• Constructed from polymer and aluminum for a durable yet lightweight stock assembly.
• Sized for mil-spec buffer tube diameter, the most common AR-15 receiver extension standard.

Frequently Asked Questions

What comes in this kit? A 6-position receiver extension, carbine buffer assembly, carbine action spring, and a 6-position collapsible butt stock assembly.

Does this fit a standard AR-15 lower? Yes, the receiver extension is sized to the mil-spec buffer tube diameter used on most AR-15 lower receivers.

Is this compatible with commercial-spec lowers? This kit is built to mil-spec dimensions; verify your lower’s buffer tube diameter before ordering if it is a commercial-spec receiver.

Buy the CMMG Collapsible Stock Kit for AR-15

Complete your AR-15 lower build with the CMMG Collapsible Stock Kit, shipped fast from our Lubbock, Texas gun shop. Combine this kit with your choice of gun parts kit from CMMG to finish your lower group in one order.