Whoever told you that you need a patternmaster to shoot waterfowl is smoking something.. Out of my Brownings and Benellis I shoot the standard IC choke tube (which is a mod wihen shooting steel shot), and they both pattern like a dream. I used to have an 870 and it didn't pattern any steel shot worth a darn, so maybe your friend was right telling you to get a patternmaster choke for an 870....LOL

Also - My shotguns all wear 24" barrels, except for my Citori (28") and one of my BPSs (26").