Diamondback Barrels AR-15 6.5 Grendel 18in Barrel Midlength 1-8 Twist Rate 5/8 X 24 TPI 6.5M18M50B8. 5 Grendel AR-15 Barrel is machined in house on state-of-the-art CNC machines and are thoroughly inspected at multiple stages of the build process to...