You did not say whether the lumps occurred before or after reloading the bullets. It sounds like something may be hanging up. The base of the bullet could be quite square, and hanging on the case mouth. In this case, chamfering the case mouth should eliminate the problem. It is possible that the expander button is the wrong size. Mike it to be sure that the manufacturer did not put in an expander for 8mm Mauser. The bullet may be tilting going into the case mouth. In this case, you may have to expand the mouth a bit more. Good luck, and let us know what solved the problem.
