Got the idea from a post on here a while back, I ground the old knob down till it was round 5/16 diameter then threaded it. The new bolt knob is made from part of what I cut from the barrel at the muzzle. I drilled and tapped it to screw onto the threaded blot handle and used red loc-tite. My barrel is now 19 1/4 inches, Overall length of rifle is 39 1/2 inches. Working on fitting that new stock