One of my buddies has that gun and has gotten good patterns out of it. I know he bought an aftermarket choke tube but I'm not sure what brand. I could ask him for you. I would strongly suggest trying a couple different tubes. I shoot an undertaker choke in my 11-87 and it patterns awesome!! I think they sell for only like $20 or so. A small fee considering what you paid for the gun. The gun should be capable of patterning well. You've tried different shells, the next step would be chokes.