One of the best lead shot 40 yard patterns I've seen, (not a Hevi-shot load), was fired from a Mossberg 500 pump. The choke tube was a Hastings non-ported extended turkey tube, in a .665 constriction, using Winchester High Velocity, (black box), 3" Turkey loads of # 5 shot in the 1 3/4 ounce payload. The choke tube's affordable, (about 23 dollars), as were the shells at under 10 bucks a box. A very lethal combination in that gun. #6 shot in the same load works well too, but you give up some down range energy with the smaller shot size. I'd stick with the 5's.