All the .50's are 1:28, not positive on the .58's but think they are 1:56.
There is an easy way to find out by putting a tight fitting patch on your jag...then inserting all the way in the barrel...put a piece of tape even with the muzzle...mark the tape in line with the sight...slowly remove ramrod until it makes 1/4 turn...or better yet if fast enough twist 1/2 turn...then measure from muzzle to tape...for 1/4 turn multiply that number by 4...for 1/2 turn multiply that number by 2. You should be able to determine exactly what your twist rate is by that method.