I think barrel length has little to do with pattern, but everything to do with handling. A 30" is going to swing smoothly and make long range hits easier on ducks, but is going to be pretty useless for snap-shooting in the North-eastern grouse woods. The guys who like to shoot those inedible clay birds have been evolving towards an average barrel length of a couple of inches longer than what was used 3 or 4 decades ago.