Quality is imbued into our barrels from the start. We start with the best materials, either certified 4150 Mil-Spec steel or 416-R Stainless. From there, each barrel goes through a battery of tests at each operation until finished in Nitride and final inspected. All barrels are individually checked for headspace by precision custom hardened gauges. Technical Specifications Barrel Material: 4150 Barrel Type: Button Rifled Barrel Caliber: 9mm SAMMI Barrel Twist: 1:10 Barrel Length: 8.5" Barrel Profile: Pistol Caliber Taper Barrel Gas System: N/A - Blowback Inside Finish: QPQ Nitride Outside Finish: QPQ Nitride Muzzle Thread: 1/2-28 TPI (Threads Per Inch) Gas Block Diameter: N/A Gas Port Diameter: N/A Gas Block Journal Length: N/A Barrel Extension: Colt & Glock Compatible Feed Ramps Weight: .81lbs 11-degree Target Crown *Note - Faxon Firearms advertises its barrels by their legal length. Pistol Caliber Carbine barrels have the chamber built into the barrel "extension" area, which makes them about ~1" shorter than centerfire rifle barrels.