I'm gonna guess your lead is too soft, add some more tin maybe. When I have had some projos that dropped out of the mould a little large (mostly LEE TL that typically don't require sizing) but for whatever reason, dropped a tad on the large side, they would bulge the sized brass at seating. It really appears your lead is too soft.
edited to add: I gotta ask, but it appears obvious you are reloading for the 9mm. Although it's not exactly a straight wall case, I have yet to see any 9mm dies that utilize expander balls. And .357 to .358 would not grip a nominal .356 projo that most 9mm's will want to be fed.
Last edited by okiefarmer; January 14, 2011 at 02:14 AM.