The shorter barrel will not be able to hold the pattern as well as the longer barrel, If you are looking for a duck hunting gun 28 or 26 inch barrels will act the same to the naked eye anyways, 21 inch is way to short for a waterfowl gun unless sucks are inside 20 yards. And as a duck hunter who hunts ALOT its hard to get them at 20 yards all the time lol