San Tan Tactical Series Ironclad 5.56 NATO Threaded AR Barrel 16 inch Mid Length Nitride Finish Black Medium. 5in Ironclad barrel provides the ideal balance of compact length and velocity for 5.56 NATO platforms. Featuring a heavy-duty Black Nitride (QPQ) finish inside and out this barrel delivers superior bore life exceptional corrosion resistance and heat dissipation. The carbine-length gas port is tuned to maintain reliable extraction and dwell time in compact duty builds. Specifications for San Tan Tactical 1836 Series Ironclad 5.56 NATO Threaded AR Barrel: Manufacturer: San Tan Tactical Color: Black Finish: Nitride Fabric/Material: 4150 Chrome Moly Vanadium Caliber: 5.56x45mm NATO Gas Block Journal Size-Diameter: .750 in Barrel Twist Rate: 1-7 Barrel Material: 4150 Chrome Moly Vanadium Flutes: No Gun Make: AR Platform Weight: 2 - 2.5 lb Gas Block Journal Size-Length: 1.13 in Gun Type: Rifle Firearms Threads Per Inch: 1/2x28 Features of San Tan Tactical 1836 Series Ironclad 5.56 NATO Threaded AR Barrel Smooth-cycling mid-length gas port design Black Nitride surface treatment for maximum thermal and wear resistance Precision-machined chamber for flawless feeding Compatible with all standard 5.56/.223 suppressors and muzzle brakes Package Contents: San Tan Tactical 1836 Series Ironclad 5.56 NATO Threaded AR Barrel San Tan Tactical STT-1836I-16B-556-N: 1836 Series Ironclad 5.56 NATO Threaded AR Barrel 16 inch Mid Length Nitride Finish Black Medium