AmericanLongRifles Forums
General discussion => Gun Building => Topic started by: Scott Bumpus on April 29, 2013, 07:58:40 AM
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How do you do the lay out to cut a gain twist into a rifling worm? I have the blank turned and most the bed made for a bookie style rifling bench. I want to try a gain twist set up.
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Draw a parabolic curve on a large sheet of paper, cut it out and wrap it on your blank. Trace the line of the edge of the curve onto the blank. Cut a grove along the line. You can repeat the process if you like to get the additional groves or you can use just one grove and index either the cutting shaft or the barrel.
A friend and I built a rifling device based on a plan he came up with which allows us to cut regular rifling right or left and gain twist right or left. We rifled a 54 Cal. barrel for a gun I'm building with 12 groves, left hand gain twist from 1:70 to 1:18 buttress rifling. We tested the barrel and it shoots great. Can't wait to get the gun finished so I can try it out as a completed rifle.
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It runs in my mind that this is spelled out in either Clines or Ned Roberts book???
Paul
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Well I went back to algebra class to remember how to lay out a parabola. Now I have to figure out how to make the parabola needed for a given twist 60" to 48" for example. Thanks for the answers. i think a little trial and error will get me there.
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May want to give Bob Hoyt a call. He does em
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Bob does a gain twist..BUT...he is doing it with a "sine bar" rifling machine. A lot easier......Don