I also recall, but don't have a link to it either, where a study was done by Winchester at Nilo Farms on ducks. Their study showed that to reliably & consistently kill ducks @ 40 yds as I recall, required 6 hits with #6 shot, 5 hits with #5 or 4 hits with #4. This was done just prior to the lead ban & was with lead shot.
A one-shot kill with any reasonable size of shot apt to be shot at game requires more luck than skill, as that one shot has to hit a vital area. There is simply no way to aim any individual pellet in a shotgun pattern. When the pattern is so thin that one is depending on 1-shot kills a passel of birds are going to fly off "Packing Lead", or steel, as the case may be to die later.
