Why now I just may try that. Semisane sent me some .575" balls to shoot out of my .58 a couple years ago and they shot great with a .018" patch. I mistakenly purchased a .570" mold and can't get near the grouping I was getting with Semi's balls. I'm going to clean the bore like above and try using .020" material. Below is a pic of the 100 yard group with Semisanes balls.
Target states .535" ball incorrectly.