See if you can get a cylinder choke tube, it will be more open then either IC or skeet. Another way you can change your pattern is the shells that you choose. Avoid trap loads as they hold tighter then some field loads. A couple of afternoons at the range pattering your gun and various loads will put you on the right track. I'm sorry but I not sure about the shims for your gun but I'm sure there are different shims which should help. Good luck.