Colin, I measured my 2 bore balls, and the balls themselves are 1.309" in diameter. I have to use a fairly thin patch at about .08" thickness to get it to fit in the 1.325" bore. The round balls weigh right at 3340 grains a piece. The regular pillow ticking that is used a lot for patches is way too thick. The material I use is almost like a really thin cloth sheet. Do you use any kind of card between your lubed patch and the powder? I use a simple index card cut round to fit.