I killed hundreds of ducks with one ounce of 5’s in my 28 as a youth. Even killed a few geese with 5’s but my father did not appreciate my doing it and I lost a whole week of hunting as punishment. I’d either go to 5’s or stick with 6’s and bump the speed up to 1200 or better yet go to 5’s at 1200. Those old Winchester 28/1 ounce were about 1150 not todays 1300 fps hot rod shells.