My wife just got a Bersa 380. I've scrounged about 900 once fired cases from our local range (I'm a rangemaster - one of the perks) of mixed manufacture. I cleaned them up real pretty, sized & decapped (RCBS dies) and primed them. Now I am flaring the case mouth prior to loading with powder & bullets. I have noticed that Federal cases have considerably more resistance when belling the case mouth. So much so that there is a bulge in the case about half way down - about where the end of the expander ball would come. All other manufacturers cases (WIN, RP, etc) do not show this problem. They run through the die with barely any resistance. Occasionally a CBC case will be stiffer but no bulge. I did have one Starline case bulge but other than that only Federal cases and without exception. I've sorted out the Federal cases and am leaving them for later when the problem is solved. So my question is what would cause the cases to bulge when all I am doing is expanding the case mouth just enough to get a bullet started? Any ideas?