I have a Model 500 .410 pump that feeds two shells at a time out of the magazine if I put more than one round in the tube. I can put one in the chamber and one in the magazine tube and use it fine as a two-shot, but if I try to put more in the magazine, it will double feed the rounds when I pump it. I contacted Mossberg and they had me send the gun back to them for repair. I am waiting to get it back now but was wondering if any of you have experienced that problem before and what you did to correct it?