How do you measure the rifling twist rate on a gun barrel?

Answer 1

Insure rifle is unloaded. You will need a cleaning rod, bit of masking tape, marker, ruler, and an oiled patch. Use tape to make a "flag" that wraps around the rod near the handle. Place oiled patch (large enough for snug fit) in the barrel, push down until tape is near muzzle. Note where tape is pointing. Mark rod with marker at muzzle. Withdraw rod, allowing it to rotate, until tape "flag' has rotated back to original direction, having made one full revolution. Mark rod again at muzzle. Measure between the two marks. If it took 12 inches of rod to turn one full revolution, that is a 1 in 12 twist- or one in 10, 1 in 6, etc. VERY slow twists for a muzzle loader may mean you use 180 degrees of rotation, and double the measurement (1 in 40, etc)