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.

FN Manufacturing 16 Inch Government Profile ( A2 ) Hammer Forged barrel. Barrel has 5.56 Nato chamber,  1/7 twist rate, M4 barrel extension, carbine length gas system, threaded ½ x 28 muzzle and Mil-Spec phosphate coated.  Barrel and chamber are chrome lined to a specification that is almost double the thickness of a standard M4/M16 Mil-Spec barrel and are stamped with the FN oval .  These barrels are hammer forged, machined, chambered, chrome lined and completely phosphated by FN Manufacturing.

18 Inch Mid-Length Fluted Stainless Steel Barrel with Extension and Pin 
.223 Wylde Chamber, air gauged, cryo-treated 1:8 twist, threaded 1/2-28, with barrel extension and pin. Weight 37.3 ounces.