The BCM MK2 Receiver Extension is an 8-position intermediate-length buffer tube for AR-15 and M4 rifles, supplied as a bare tube with no buffer, no action spring and no stock.
This is the point people get wrong, so it is worth being blunt about it. The MK2 is an intermediate-length receiver extension: longer than a carbine tube, and designed around a longer spring and a purpose-made buffer. Dropping in the carbine buffer and carbine spring from your existing build will not give you a working rifle. You need a BCM MK2 buffer and an M16 rifle action spring to go with it. If you would rather buy the tube, buffer, spring, castle nut and end plate as one matched set, the BCM MK2 Recoil Mitigation System Mod 1 does exactly that; and if the MK2 tube is already in the rifle and you only need the buffer itself, that is the BCM MK2 Buffer Mod 1.
With the correct parts in it, the MK2 is a well-made tube: machined from 7075-T6 aluminum, hard coat anodized to Mil-A-8625F Type III Class 2, cut to Mil-Spec dimensions but with a slightly smaller dimension where the stock slides on, which is what removes the stock wobble that plagues ordinary tubes. The interior is given a dry lube spray coating. It offers eight stock positions rather than the usual six.
How It Compares
Supplied as a tube only. You must add an MK2 buffer and an M16 rifle action spring — a carbine buffer and carbine spring will not function in it — and the castle nut, end plate and stock are also not included.
Key Features
- Eight positions — finer length-of-pull adjustment than a six-position carbine tube
- Tightened stock interface — a slightly smaller sliding dimension takes out stock wobble
- 7075-T6, hard coat anodized — Mil-A-8625F Type III Class 2
- Dry lube interior coating — applied from the factory
- Takes standard Mil-Spec stocks — USGI, BCM, Colt, LMT, SOPMOD, VLTOR and Stag Arms
Compatibility & Fitment
Threads into AR-15/M4-pattern lower receivers with a standard threaded rear, and Bravo Company USA states it is usable on most AR-10 platforms as well. It takes Mil-Spec dimension stocks from USGI, BCM, Colt, LMT, SOPMOD, VLTOR and Stag Arms. Fitting needs a castle-nut wrench, and the nut should be torqued and staked or thread-locked.
Technical Specifications
Platform | AR-15 / M4; usable on most AR-10 platforms |
Fits | Lower receivers with a standard threaded rear; Mil-Spec stocks from USGI, BCM, Colt, LMT, SOPMOD, VLTOR, Stag Arms |
Type | Intermediate-length receiver extension, tube only — requires an MK2 buffer and an M16 rifle action spring |
Material | 7075-T6 aluminum |
Finish | Hard coat anodized, Mil-A-8625F Type III Class 2 |
Adjustment | 8 stock positions |
Brand | Bravo Company USA |
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
Can I use my existing carbine buffer and spring in this tube?
No. This is the single most important thing to know about the MK2. It is an intermediate-length receiver extension and it requires an MK2-specific buffer together with an M16 rifle-length action spring. A carbine buffer and carbine action spring will not function in it. Fit the wrong parts and the rifle will not work. If you want the whole assembly matched from the factory, the BCM MK2 Recoil Mitigation System Mod 1 supplies the tube, buffer, rifle action spring, castle nut and QD end plate together.
What exactly is in the box?
The tube on its own. There is no buffer, no action spring, no castle nut, no end plate and no stock.
Which stocks fit it?
Mil-Spec dimension stocks, including USGI, BCM, Colt, LMT, SOPMOD, VLTOR and Stag Arms. The sliding surface is cut slightly smaller than a plain Mil-Spec tube, which is deliberate: it takes the wobble out of the stock rather than making it incompatible.
