Reloading new Starline brass with Hornady 250 gr. Monoflex bullet. Purchased new set of RCBS dies. Have resized and trimmed all cases. I am experiencing a consistency issue with expanding the case mouth. Instructions say bullet base should snap into case mouth and if not set die deeper. None of the expanded cases seem to be uniform. First on allows snap in, second admit the base but very snugly, third not at all. The die is properly locked and tightened; all cases receive a full stroke on the press with no issue. Any idea why there is not consistency? Thanks.