I've been shooting .570 round balls with .010 Ox-Yoke patches, and it's a tight fit, yet the patches are still blowing through because they are too thin. I'm wondering if maybe it's the rifling still being too new that is tearing them. In any case, I was thinking of trying the .562 ball from a friends Lee mold with thicker patches. I had the bore gauged and it was indeed .580 (Armi San Paolo made in 1975). It is 5 groove 48" twist. Would appreciate any thoughts on this.