BCM MK2 Recoil Mitigation System Mod 1 for AR-15

The BCM MK2 Recoil Mitigation System Mod 1 is a complete buffer system for AR-15 and M4 rifles, supplying the MK2 buffer, an M16A4 rifle action spring, the MK2 receiver extension, a castle nut and a QD end plate in one kit.

Everything the conversion needs in one box — buffer, rifle spring, 8-position tube, castle nut and QD end plate. Fit it and the rear of the rifle is done.

This is the complete system, not a component. Five parts ship together: the MK2 Mod 1 buffer at your chosen weight; a Mil-Spec M16A4 rifle action spring with more coils than an M4 carbine spring; the MK2 receiver extension, 7075-T6, 8-position, Mil-Spec diameter and approximately ¾" longer than a carbine tube; an M4 castle nut; and a receiver QD end plate with an integral QD swivel mount. If you only want the buffer — because the MK2 tube is already in the rifle — the bare component is the MK2 Buffer Mod 1, which is the same buffer at a very different price.

The engineering is in the pairing. The intermediate-length tube gives the buffer more room, the buffer runs a longer internal counterweight travel with an internal spring to quieten it, and the longer rifle spring with its extra coils widens the operating envelope and steadies carrier velocity. Together they reduce bolt bounce and give a more consistent return to battery. It is covered by BCM US Patent 10415907.

On a UK straight-pull AR-15 the appeal is different from the American one and just as real. You work the action by hand, so the mass of the buffer and the rate of the spring are exactly what your hand feels on every stroke and exactly what governs how positively the carrier goes back into battery. The three weights let you set that feel: T0 at 3.8 oz (110 g) is the lightest stroke, T2 at 5.6 oz (160 g) the most deliberate. The QD end plate in the kit also gives you a sling point at the rear of the receiver without buying one separately.

Why shooters choose the MK2 Recoil Mitigation System

• Complete five-part kit — buffer, rifle spring, MK2 receiver extension, castle nut and QD end plate
• Intermediate-length tube — approximately ¾" longer than carbine, giving the buffer more travel
• M16A4 rifle action spring — more coils than an M4 carbine spring for a wider operating envelope
• Three buffer weights — T0 3.8 oz (110 g), T1 4.7 oz (135 g), T2 5.6 oz (160 g)
• QD end plate included — a rear sling point comes with the kit rather than as an extra

What the MK2 Recoil Mitigation System fits

Fits AR-15/M4 lower receivers that take a Mil-Spec-diameter receiver extension, including UK straight-pull AR-15 builds, and replaces the existing tube, spring, buffer, castle nut and end plate entirely. One fitment caveat matters: because the MK2 extension is approximately ¾" longer than a carbine tube, some Mil-Spec stocks will not collapse all the way back to the castle nut — the stock still works, it simply will not close fully. Commercial-diameter tubes are a different specification and are not what this kit supplies. The buffer, spring and tube in this kit are designed as a set: do not mix the MK2 buffer with a carbine spring or a carbine tube, as BCM states that incompatible combinations can damage the rifle and injure the operator.

Specifications

One box, one job, done properly. Order the MK2 Recoil Mitigation System today — in stock at Xtreme Tactical Gun Parts with free tracked UK delivery in 7–10 days.

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