To check your rifling twist, you could push a tight fitting oiled patch through the bore on a wooden dowel rod. You would put a pencil line on the rod at 12:00, and then push it through with a live center from a small lathe. The live center will permit the dowel rod to rotate along with the rifling. If the length of your bore from end of chamber to muzzle is 25", and the index mark on the dowel rod rotated one full turn, that would indicate a 1 in 25" rate of twist. Half a turn over the same distance would indicate a 1 in 50" rate of twist.
You could also mark the rod at the point where you started pushing at the beginning of the rifling, and then mark the point where it made one full turn, and then measure the distance between those two marks.
