BCM MK2 Recoil Mitigation System Mod 1 for AR-15
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Fits AR-15/M4 lower receivers taking a Mil-Spec-diameter receiver extension, including UK straight-pull AR-15 builds. Replaces the existing tube, spring, buffer, castle nut and end plate. Because the MK2 extension is approximately ¾" longer than a carbine tube, some Mil-Spec stocks will not collapse fully back to the castle nut. Do not substitute a carbine spring or carbine tube.
Not sure it fits your rifle? Ask us before you order
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.
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.
| Platform | AR-15 / M4 |
|---|---|
| Fits | AR-15 / M4 lower receivers taking a Mil-Spec-diameter receiver extension |
| Type | Complete recoil system — MK2 buffer, M16A4 rifle action spring, MK2 receiver extension, castle nut and QD end plate |
| Material | Buffer 7075-T6 aluminium; MK2 receiver extension 7075-T6 aluminium |
| Finish | Hard-coat anodised |
| Weight | Buffer T0 3.8 oz (110 g) · T1 4.7 oz (135 g) · T2 5.6 oz (160 g) |
| Length | MK2 receiver extension approximately ¾" (19 mm) longer than a carbine extension |
| Adjustment | 8-position receiver extension |
| Brand | Bravo Company USA |
| MPN | BCM-MK2RMS-M1T0 · BCM-MK2RMS-M1T1 · BCM-MK2RMS-M1T2 |
One box, one job, done properly. Order the MK2 Recoil Mitigation System today — imported from the USA with all duties paid by us and dispatched tracked from the UK in 7–10 business days, with nothing to pay on delivery.
Explore more: AR-15 Parts & Accessories, Rifle & Shotgun Stocks or browse all Bravo Company USA.
| Platform | AR-15 / M4 |
|---|---|
| Fits | AR-15 / M4 lower receivers taking a Mil-Spec-diameter receiver extension |
| Type | Complete recoil system — MK2 buffer, M16A4 rifle action spring, MK2 receiver extension, castle nut and QD end plate |
| Material | Buffer 7075-T6 aluminium; MK2 receiver extension 7075-T6 aluminium |
| Finish | Hard-coat anodised |
| Weight | Buffer T0 3.8 oz (110 g) · T1 4.7 oz (135 g) · T2 5.6 oz (160 g) |
| Length | MK2 receiver extension approximately ¾" (19 mm) longer than a carbine extension |
| Adjustment | 8-position receiver extension |
| Brand | Bravo Company USA |
| MPN | BCM-MK2RMS-M1T0 · BCM-MK2RMS-M1T1 · BCM-MK2RMS-M1T2 |
| Category | Lower Parts |
| Barcode | 812526023100 |
£5 tracked UK delivery on every order via Royal Mail Tracked 24. Our products are ordered in from the manufacturer rather than held in UK stock, so please allow 7 to 10 business days (Monday to Friday, excluding bank holidays) from the date of your order for it to reach you. Tracking details are emailed on dispatch. UK delivery only.
You have 30 days from receiving your order to cancel it for any reason, then 14 days to send it back unused and in its original packaging. Faulty, damaged or incorrect items are replaced or refunded and we cover reasonable return postage. Refunds go back to your original payment method within 14 days of receiving the return.
Five parts: the MK2 Mod 1 buffer in your chosen weight, a Mil-Spec M16A4 rifle action spring, the MK2 receiver extension (7075-T6, 8-position, Mil-Spec diameter), an M4 castle nut, and a receiver QD end plate with a QD swivel mount. A stock is not included — you fit your existing stock to the new tube.
The <a href="/products/bcm-mk2-buffer-mod-1">MK2 Buffer Mod 1</a> is the bare buffer on its own, for shooters who already run an MK2 receiver extension and want to change weight or replace a part. This listing is the complete system and includes that same buffer plus the tube, spring, castle nut and end plate. Same T-numbers, very different contents and price — if you are converting a standard carbine rifle, this is the one you want.
T0 is 3.8 oz (110 g), T1 is 4.7 oz (135 g) and T2 is 5.6 oz (160 g). More mass means a more deliberate stroke and more resistance to bolt bounce; less mass means a lighter, quicker stroke. On a straight-pull AR-15 worked by hand, this is largely a question of the feel you want under the palm, and T1 is the sensible middle if you have no preference.
Your stock fits, because the MK2 extension is Mil-Spec diameter and 8-position. It may not collapse completely: the tube is roughly ¾" longer than a carbine extension, so some Mil-Spec stocks stop short of the castle nut at the closed position. Everything else about the stock works normally.
Buffer systems are sent from the United Kingdom with £5 tracked UK delivery in 7–10 business days, and you will get tracking by email when it ships. If a part turns out to be the wrong fit, see our returns policy or <a href="/pages/contact">contact us</a> and we will help sort it.
7 to 10 business days from the date of your order. Every order is sent Royal Mail Tracked for a flat £5 and you receive tracking details by email when it is dispatched.
Yes. We list only genuine parts and optics from the brands shown, ordered in from the manufacturer for your order.
Compatibility notes on this page come from the manufacturer. If you are unsure, email us with your make and model before ordering and we will check rather than guess.
Yes. Bundle & Save applies automatically in your basket: 5% off when you buy 2 items, 10% off at 3 items and 15% off at 4 or more. It works across the whole range, so you can mix and match, and there is no code to enter.
Yes — you have 30 days from delivery to cancel for any reason, as long as the item is unused and in its original packaging. See our returns policy for the details.
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