The Griffin Armament HEDP(TM) Barrels provide High Endurance Dual Purpose functionality- offering high durability and precision accuracy. 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(TM) 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 and unsuppressed with both supersonic and subsonic ammunition. A medium 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 ...