This video is well worth a watch to help you figure out how your various duck load options perform as to the length of the shot string in your guns/shells. He has filmed shot strings with a camera that takes pics at 180,000 pics per second. The video using many brands and loads shows shot strings with all shot impacts within 6 feet of target and some that are 16 feet long . I always thought I wanted all shot on target in the shortest interval. I still do after watching this. But some higher dollar shells are not providing that impact. Some cheaper ones are superior in length of shot string.
When we pay what we do for waterfowl loads we expect better performance with more expensive shells. We may have been getting fooled by just looking only at how many pellets are in a stationary piece of paper. When those pellets get to a point of impact on a fast moving target may be a critical component of determine what duck load we should be choosing?