I have a .22 cal. shotgun with no rifles in the barrel. The choke opening measures .385 in or 9.71 MM. Shoots "22 long shot". I know this is a silly question but what choke would this equal? This gun was made by Stoeger Arms Corporation of New York, with ZEPHYR on barrel. Action by J. G. Anschutz.Should make a good kids target gun. Or rat killer supreme.