Single Stage press or Progressive?
If Progressive are you seating in one step and crimping in another? If not you should.
If you are shooting jacketed bullets your bell should be just enough for the bullet to sit in the bell, that is the best advice, just do this. If you are shooting lead or moly coated lead, put a little more bell on your brass.
If you are crushing the case it could be from too much bell or not enough or from seating/crimping in one step instead of two, I have done it all three ways!