I think I figured it out, it came to me while I was on my morning run. The bullet seating die is too long creating a small gap between the case and the shoulder area of die. When the bullet is seated the pressure form the seating process is bulging the base of the shoulder (see picture). I am going to take .005" off of the bottom of the seating die to see if that reduces the bulge. If it works I will post my findings as I go.