Mil-spec buffer tubes have a slightly smaller outer diameter (1.148”) and are slightly tapered, while commercial-spec tubes are larger (1.170”) and straight. Most quality AR-15 carbine stocks — including Magpul, B5 Systems, and others — are available in both specs. The CMC 81626 is mil-spec. When ordering a stock separately, make sure to match the spec to this tube.

No. The 3 oz. carbine buffer and spring included in this kit are specifically tuned for .223/5.56 cycling. Using them in a .308 / AR-10 build will result in unreliable feeding and extraction. AR-10 platforms require a heavier buffer (typically 3.8–5 oz.) and a rifle-length buffer system.

CMC’s design extends the bottom lip of the buffer tube further into the lower receiver compared to standard designs. This provides additional structural support at the receiver interface — the point that absorbs recoil energy on every shot. The result is a more robust connection that’s less susceptible to stress fractures over high round counts.

This kit includes every component of the buffer system except the stock itself. The tube, buffer, spring, castle nut, lock ring, and QD end plate are all included. Simply add your preferred mil-spec carbine stock and you have a complete assembly ready to install on any mil-spec AR-15 lower receiver.

The included QD receiver end plate features quick detach (QD) sling swivel slots, compatible with standard push-button QD swivels found on most two-point and single-point sling systems. This allows you to attach and remove your sling without tools and without stressing fixed sling loops.