I make hardened file trim dies for the purpose. A couple of guys here use them. If you feel the need to do it, first hand file a few to try and see if it works for you. Use a mic or dial caliper to gauge yourself. (We're talking naked bullets here, not ones already stuffed in a case.)

"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty