The BCM MK2 Receiver Extension (brand part number BCM-MK2-RE) is a mil-spec-dimension buffer tube from Bravo Company machined from 7075-T6 aluminum for the AR15, M16, and M4 platforms. It’s built specifically to work with BCM’s MK2 buffer system rather than as a general-purpose receiver extension, and the diameter where the stock rides is held to mil-spec tolerance so it works with any standard mil-spec collapsible stock. Because the MK2 system relies on a specific rifle action spring paired with a matching MK2 buffer, this extension is not a drop-in match for standard carbine or rifle buffers.

Key Specifications

• Machined from 7075-T6 aluminum for strength and long-term durability.
• Held to mil-spec dimensions, including the slightly smaller diameter where the stock rides.
• Built to work with a BCM MK2 buffer and rifle action spring, not standard carbine or rifle buffer springs.
• Compatible with the AR15, M16, and M4 platforms.
• Requires the matching MK2-specific buffer; standard carbine and rifle buffers will not function correctly with it.

Frequently Asked Questions

Will a standard carbine buffer work with this receiver extension? No. BCM specifies that this extension requires a rifle action spring and a specific BCM MK2 buffer; standard carbine and rifle buffers will not work correctly with it.

What stocks fit this receiver extension? Any standard mil-spec collapsible stock, since the extension is held to mil-spec dimensions, including the diameter where the stock rides.

What material is it made from? 7075-T6 aluminum, machined to mil-spec dimensions and tolerances.

Buy the BCM MK2 Receiver Extension

Build the foundation of a proper MK2-tuned buffer system with the BCM MK2 Receiver Extension. Order it from our Lubbock, Texas gun shop for fast, insured shipping and complete your AR-15 buffer system upgrade.