I have not had much help from Mossberg on this issue. I have a mossberg 835 ulti mag turkey gun from about 2001. It has three unmarked choke tubes. If I wanted to shoot buckshot, which tubes do I need? MB says to use only modified and improved cylinder "ulti mag" tubes but I only see a full choke in the ulti mag line. I want to shoot 3 inch buck shot from this shotgun. They also say their tubes are all plainly marked so maybe i have aftermarket tubes. There are no factory marks on the existing tubes.