I have had that happen with Winchester straight-walled, rimmed cases. .44 Spl. and .357. I noticed it with brand-new, unfired cases. I had to dress down the head area with a smooth file to get them to fit the shell holder. Only a few out of each 50 round batch. For this and other case-dimension inconsistencies, I avoid buying Winchester pistol (and rifle if I can find an alternative),cases.