BCM MK2 Buffer Mod 1 for AR-15

The BCM MK2 Buffer Mod 1 is a bare intermediate-length buffer for AR-15 and M4 rifles, sold on its own for shooters who already run the BCM MK2 receiver extension.

The two BCM part numbers look alike and are not alike: this listing is the bare BFMK2 buffer, with no receiver extension, no spring, no castle nut and no end plate. If you do not already have a BCM MK2 receiver extension and a Mil-Spec M16 rifle action spring in the rifle, this part will not fit anything you own. You want the complete MK2 Recoil Mitigation System Mod 1, which contains this same buffer along with the tube, the rifle spring, the castle nut and the QD end plate.

What you get is the mechanism itself. The MK2 buffer is machined from 7075-T6 aluminum and hard-coat anodized, and it runs a longer internal counterweight travel than a carbine buffer with an internal spring to quiet the counterweight as it shifts. Longer travel means less bolt bounce and a more consistent carrier velocity, which BCM covers under US Patent 10415907.

Buffer weight is the tuning lever. T2 is 5.6 oz (160 g) and T4 is 7.4 oz (210 g), and the heavier the buffer the more mass has to be moved and returned on every stroke.

Key Features

• Bare buffer, sold alone — the correct part when you already run an MK2 system and want a different weight
• Increased counterweight travel — reduces bolt bounce and steadies carrier velocity
• Internal spring — quiets the counterweight as it shifts
• 7075-T6, hard-coat anodized — the same construction standard as BCM's complete system
• Two weights — T2 at 5.6 oz (160 g) and T4 at 7.4 oz (210 g) to tune the stroke

Compatibility & Fitment

This buffer fits the BCM MK2 receiver extension only, and must be run with a Mil-Spec M16 rifle action spring. It is not a carbine buffer and will not work in a standard carbine receiver extension, and a carbine spring must not be substituted — BCM is explicit that incompatible components can damage the rifle and injure the operator. If you are starting from a standard carbine buffer system, choose the complete MK2 Recoil Mitigation System Mod 1 instead; it includes this buffer plus everything else the conversion needs. One further note on the MK2 tube itself: because it is roughly ¾" longer than a carbine extension, some Mil-Spec stocks will not collapse all the way back to the castle nut.

Technical Specifications

US Shipping & Support

Shipped from D&R Sports Center in the USA with fast, tracked delivery. Questions on fit, mounting or which model suits your setup? Our team is glad to help before and after your purchase.

Frequently Asked Questions

Is this the complete recoil system or just the buffer?
Just the buffer. This listing is the bare BFMK2 component — there is no receiver extension, no action spring, no castle nut and no end plate in the box. The complete kit is the MK2 Recoil Mitigation System Mod 1, which contains this same buffer plus all four of those parts.

Will it fit my standard carbine buffer tube?
No. The MK2 buffer is intermediate length and is designed for the BCM MK2 receiver extension with a Mil-Spec M16 rifle action spring. It will not work in a carbine receiver extension, and BCM warns that running incompatible buffer, spring and tube combinations can damage the rifle and injure the shooter. Check what is in your rifle before ordering.

Should I choose T2 or T4?
T2 is 5.6 oz (160 g) and T4 is 7.4 oz (210 g). Heavier means more mass to move and return on each stroke; lighter means less. If you are replacing a buffer in an existing MK2 system, match or step from what you already have. If you are unsure which weight is in your rifle, weigh the buffer you take out.