.17 Cal, 1:9 Twist, 4140CM. 25"overall length with a 77/22 taper. Includes a 1.06" diameter, 1.25" long round breech end and dual taper octagon profile with diameters of .835" to .660" at 4.125" inches then straight taper to .630" at the muzzle. Octagon Barrel Blank. Button Rifled, Air Gauged, and Stress Relieved.