This is a .40S&W case sized using RCBS dies. It most likely has been loaded a few times. When I tried to size, it took too much force then finnally stopped before the case would go all the way into the die. It has left a 'ridge' on the case. I had this happen about 3 times out of 200 cases. My question is, what is causing this??? Does my die need to be cleaned?? Case not clean enough?? Has the case been loaded too much?? Thanks for your help.