The utility of 5.56mm is hard to beat. If you want a .22 caliber round that reaches out further for target shooting or varmint hunting then 22 ARC is what you need. - Designed for the AR15 platform this 16.1 22 ARC barrel is ready for your next build. - Caliber .22 ARC - Barrel Length 16.1 - Barrel Twist 1:7 - Barrel Contour MT - Barrel Material 4140CM Nitride Finish - Barrel Twist 1:7 - Muzzle Thread 1/2 x 28 - Gas Port Location Rifle