OK, I tried! Using the technique described, I can see no rotation. Possibly because the rifling is so shallow, and very smooth. If I try to figure this, I come up with maybe 1 in 54"??? I could be way off! It looks like 1/4" rotation in 6", if the circumference is 2.3", that would be 1/9th of a turn in 6"? This is all kind of a guess, and my math could be way off.

Best guess! Doug