How is it that the centrifugal force does not just lodge the cases in a lump in on spot of the drum at that high an rpm? My tumbler's drum rotates at 46 rpm, which allows the cases to be constantly rolling to the bottom of the drum, thus scrubbing against the pins. If 500 rpm is the correct rpm, I'm guessing that you have some sort of mechanical agitation mechanism rather than depending on gravity to pull the cases and pins to the bottom of the drum. A picture, or better yet a video of your system would be most enlightening.