I have had that happen with only Redding dies for some reason. I also own Lee and RCBS. I take an old bore brush of a bit smaller size, wrap 0000 steel wool around the brush, put some Flitz polish compound on it and spin with a drill. That has fixed mine and it does not seem to occur again once I do that. I have shied away from Redding because of that, but I guess it happens with other manufacturers.