ReDoT, from the results you posted I would bet regular old 2-3/4" Remington Sluggers or Reduced Recoil Sluggers would have faired better than most. Maybe a 3rd, 4th place finish?

Have to ask though - were you cleaning your barrel often and starting each type of slug with a fresh clean & cooled barrel?

Also are not the faster slugs better in rifling which is slower like your Hastings?

When you posted "wouldn't group into a 5 gallon pail", I had to laugh! I can shoot standing with any of my smoothbore pumpsand put fosters into a 5 gal pail at 50 yards.