I can not located the original manual for my old 50 cal. CVA Hawken. I'm guessing it's a 1:48 twist. I thought Iwould take the jag, shove a patch a few inches down the barrel, mark the rod at the muzzle and on its side near the top, then gently run the rod down the barrel until the top mark rotates 180 degrees, measure the length of rod movement and double this to get the twist rate. Anyone ever done this? Will it work?