I agree, the reason for pattern testing to show how a particular load works in a particular gun. Slugs don't necessarily shoot straight out of a gun, nor does buckshot for that matter. Pattern test using the loads you shot last year and see where you point of impact versus point of aim are. Do this with enough shotguns and you'll soon realize most didn't hit where they are pointed. My Marlin, Boito and El Faisan all hit at different spots on a pattern board, different chokes can change point of impact due to producing more or less fliers, etc. The stock may have caused part of this issue and may need to be adjusted for fit to you and the gun. Also you may have had the same point of impact last fall with this gun without realizing it, it doesn't take many pellets to down a bird remember. All points to ponder.