Just enough crimp to remove the mouth belling.

If you crimp a lead bullet hard what you end up with is a bullet that is squeazed down in diameter while the brass springs back a bit leaving a loose bullet. It you are using a lead bullet it should be about .001" (.452")oversized anyhow giving a good tight fit in the case. My cast loads are sort of a coke bottle in shape, but they function flawlessly and are very accurate.