maybe I missed it but I don't see you mentioning moon clips. The 610 was designed to work with the clips although mine every other one I have fired/worked on will allow rounds to be fired without them. The problem with doing so is the firing pin strike forces the round forward into the chamber until it meets firm resistance and the primer ignites. When the case mouth expands it is too far forward and causes extraction issues. Try moon clips and see if this doesn't help your problem.