Rock River Arms 18 Inch Mid Length Fluted No Font Sight

5.56mm NATO Chamber, 1:9 twist, threaded 1/2-28, with barrel extension and pin. Weight 37.9 ounces.

Rock River Arms 16 inch Mid Length Fluted Barrel No Front Sight 

5.56mm NATO Chamber, 1:9 twist, threaded 1/2-28, with barrel extension and pin. Weight 35.2 ounces.

Rock River Arms 16 inch Air-Gauged, cryo-treated, Stainless Steel, Fluted, H-Bar barrel chambered in .223 Wylde with a 1:8 twist, .750 gas journal diameter, mid-length gas system, and a 1/2x28 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.

5.56mm Lo-Pro Gas Block Barrel with Switchblock®

Cold Hammer Forged, Chrome Lined Barrel -5.56mm

--1 in 7" twist 
--Extended feed ramps 
--Manganese Phosphate finish 
--Pinned Switchblock
--1/2x28 threads 
--Light Contour

 To allow access to the Switchblock®, it cannot be covered up by a handguard. The longest handguard that can be used with a carbine gas system is 7" and a 9" for the mid-length, intermediate, and rifle length.