Stern Defense AR Barrels Features The Stern Defense AR Barrels 9mm 4 is machined from 4150 chrome-moly steel a material chosen for its strength and heat resistance under repeated firing cycles. The 1 in 10 inch twist rate is matched to common 9mm bullet weights stabilizing projectiles through the short bore for consistent accuracy at carbine ranges. A black Melonite finish coats the barrel inside and out improving corrosion resistance and reducing friction for smoother cycling over time. Built specifically for the 9mm AR platform this barrel is sized to work with compatible bolt carrier groups and magwell blocks in a pistol-caliber carbine build. The barrel threads at 1/2x36 a dedicated 9mm pistol-caliber pitch that accepts compatible muzzle devices and suppressor mounts built to that same standard. At 4 inches it suits a short maneuverable PCC build intended for home defense range use or a lightweight truck gun configuration. Made in the U.S.A. the Stern Defense barrel is finished to tight tolerances for drop-in installation on compatible 9mm AR uppers. For a compact reliable 9mm AR build the Stern Defense AR Barrels 9mm 4 Threaded Barrel is available for sale at GrabAGun. Stern Defense AR Barrels Specifications Manufacturer: Stern Defense Model: AR Barrels Caliber: 9mm Barrel Length: 4 Twist Rate: 1:10 Material: 4150 Chrome-Moly Steel Finish: Black Melonite Thread Pitch: 1/2x36 Country of Origin: Made in the USA Available At: GrabAGun