News to me. I have never, ever heard of, or read of, or viewed such a thing in over 45 years of shooting, reading gun publications, and (more recently) watching You Tube videos. A patched round ball is a must in a single shot muzzle loading pistol, just as it is in a rifle, because they are identical in all but barrel length and stock. In a revolver it's going to do pretty much what Noelf2 illustrates in Post #21. It's pointless and potentially unsafe.