The two top chokes today for most guns on the market are the Pure Gold that has been on top of any testing I've done and Indian Creek
Both chokes should be in the .665 -.670 constriction Hevi shot seems to be the anwser with these constrictions and found that Hevi *13 3inch #6 in 2 oz loads shot patterns that would work out past that 40 yard range with no questions asked...
Hope that help you get started...