The choke tube thread pattern on all Weatherby shotguns is Briley compatible. You can find an extra full choke on weatherby's website. Or you can go google Briley chokes and see what you can come up with. If you are not patterning well, try different turkey loads. If you are shooting inexpensive shells, sometimes they pattern horribly out of a given gun. Try some expensive turkey loads, because they will still be cheaper than a $50 choke.