I'm having problems with the Lee 6-cavity sprue plate. The cast bullets have a tit on the base where the sprue is cut off and I can't get it to cut cleanly.......I have two old RCBS molds that I use most of the time in .44 & .45 Colt with no problems, but this Lee Mold is for use in the 45 Colt Uberti lever action rifle (255 gr RNFP). What do I need to do to get a clean sprue cut? Thanks in advance for any advice.