Daniel Defense
Daniel Defense's 11.5" Government profile cold hammer forged 5.56 barrel on carbine gas, sold stripped or with a low-profile gas block or front sight base.

The 11.5" Government profile barrel is Daniel Defense's carbine-gas short barrel, the length that sits between the 10.3" CQBR spec and a 12.5". Daniel Defense cold hammer forges it from 4150 Chrome Moly Vanadium steel, chrome lines the bore, and finishes the exterior in mil-spec heavy phosphate.
Gas is carbine length over a .750" journal, so it accepts any standard .750" low-profile gas block. Daniel Defense sells the barrel in three configurations: stripped at 1.28 lbs, with a low-profile gas block at 1.36 lbs, and with a front sight base at 1.59 lbs. The muzzle is threaded 1/2x28 and the barrel extension is A4.
Compared to the 10.3", the extra 1.2 inches buys a little velocity and a slightly softer gas curve while keeping the rifle short enough for vehicle and interior work. Compared to a 12.5", it clears a 9.5" to 10.5" rail with room for a pinned gas block. Any 11.5" build is a short-barreled rifle once a stock goes on it, so the lower has to be registered first or the firearm has to stay in a pistol configuration.
Add the Daniel Defense 11.5" 5.56 Government CHF Barrel to your build and see how it enhances your platform.