CMMG 8 inch, 4140 chrome-moly, medium tapered profile, salt bath nitride finished barrel chambered in 300 AAC Blackout with a 1:7 twist, pistol length gas system, and a 5/8-24 threaded muzzle. 

The Noveske 16 Inch Stainless Steel, lightweight contour barrel features 1:7 twist improved polygonal rifling, a 5.56mm Noveske Match Mod 0 chamber, mid length gas system, extended M4 feed ramps, bead blasted finish, 1" long gas block seat, pinned low profile gas block, and a 1/2-28 threaded muzzle.  

Comes complete with lo-pro gas block, gas block pin, gas tube and gas tube roll pin.

Daniel Defense 16 inch Cold Hammer Forged, lightweight profile barrel.  Machined from ordnance-grade 4150 Chrome Moly Vanadium alloy steel for exceptional strength, and magnetic particle inspected (MPI) to ensure there are no internal flaws in the metal.  Chrome lined 5.56 NATO bore and chamber, M4 ramped barrel extension with 1:7 twist rate, .750 diameter gas block journal, carbine length gas system, and 1/2-28 threaded muzzle.

Rock River Arms 20 inch, air-gauged, cryo-treated, stainless steel, HBAR barrel, chambered in .223 Wylde with a 1:8 twist, .750 gas journal diameter, rifle-length gas system, and a 1/2-28 threaded muzzle.

The .223 Wylde chamber was designed as a match chambering for semi-automatic rifles. It will accomodate both .223 Rem and 5.56mm NATO ammunition. It is relieved in the case body to aid in extraction and features a shorter throat for improved accuracy.