arffslug, I too shoot a SBE, and when I bought my gun, the guy sold me either an x-full or xx-Full browning choke to go with my gun(i cant remember). Im not sure what the diameter is, but with Win HV Supreme # 6, I have killed 2 birds at 53, 54 steps, and numerous ones between 35-45 yards. Knock on wood, I havent missed yet. No scope, no after factory sights. Im pretty satisfied with my set up!