People will get on me for the pic, but the largest was a 1400 pound Shire stallion who had broken a leg when it tried to get out of a box trailer that was moving it away from its home farm to a new place, I believe it was a 2 year old, but it was down and thrashing and the only gun I had in my truck was a 20 double and a couple of old Super x fosters. one in the ear finished that. Not one of my proudest moments, but it was the biggest thing I have shot with a slug.
Father in law used one to put down a 2400 lb bull that something go wrong in its gut, He liked the longer barrel to stay out side the swing of the polled head.