The problem may not be in shooting the longer shells per se, but with the length of the ejection port. I have a short chambered model 12-16 ga. that won't eject anything reliably but the 2.5" shell. Buy the short shells from RST/Polywad or the Kent Gamebore. Your not giving up anything by shooting the shorter shell, save the empties and use those for your reloads.

CH


Cameron Hughes