Griffin Armament 16.1 inch 223w HEDP Barrel w/Gas Block. Nitrided 416R stainless steel provides the highest possible hardness and longest throat life available with match grade bore dimensions and bore finish. HEDP barrel bores are hand lapped ensuring batch to batch consistency and accuracy. TRUE-BORE concentric suppressor grade threads provide an optimized thread interface for your silencer regardless of brand or model. M4 feed ramps and chambers are polished prior to nitriding for smooth reliable feeding chambering and extraction. Gas ports were carefully engineered to provide reliable function suppressed or unsuppressed with 5.56 NATO ammunition. M4A1 contour diameter between the chamber and gas block for minimal POI shift with suppressors and maximum accuracy and durability while maintaining field weight. The included 416R Low profile Griffin Armament Primo gas Block offers unmatched value in the interest of increased customer satisfaction. Threads are slotted for pinning and welding your favorite Griffin Armament muzzle device. The PRIMO Gas Block can be pinned by a trained gunsmith. Alternatively end users can quickly mount their block with the included set screws. Proficient builders should use a carbide tipped 1/8 inch drill bit to complete the pin hole prior to pressing the included splined pin. (splined pin installation is optional) 416R SS barrel manufactured from stress relieved certified barrel steel. Black nitrided for extended service life. Magnetic particle inspected. Button rifled. 223 Wylde chamber for optimal accuracy. Softer recoil characteristics. .750 inch gas block journal. M4A1 diameter for reduced POI shift / Increased Accuracy and Durability. Air gauged and hand lapped bore. Polished chamber and M4 feed ramps. TRU-BORE suppressor quality threads. Suppressor optimized gas ports. .625 inch 1/2x28 industry standard threads. threads pre slotted for pin and weld applications. Included 416R Low Profile PRIMO Gas Block. 1/8 Twist. Specifications for Griffin Armament Griffin 223 Wylde HEDP Barrel w/Gas Block: Manufacturer: Griffin Armament Finish: Black Nitride Caliber: 5.56x45mm NATO Barrel Profile: M4 Barrel Twist Rate: 1-8 Condition: New Package Contents: Griffin Armament Griffin 223 Wylde HEDP Barrel w/Gas Block Griffin Armament HE161223W: 16.1 inch 223w HEDP Barrel w/Gas Block