I shoot mainly Win. LB and always seem to have difficulty figuring what choke constriction I should use/try. Found this APP the other day and have not seen it on the forum before. Maybe some others may find it useful as there are always questions about choke constriction on the forum. It has helped me select a couple of chokes. just remember this is just a starting point and only field practice will provide the infinitive answer.
http://patternboard.winchester.com/#/