Back when my hair wasn't mostly white, I shot with friends at a home range nearby. We had a beer keg set up at 130 yards, as far as we could shoot there. Used it like a gong. To hit with a slug, we had to aim at the top to hit low, near the middle.
At a Redneck Jamboree a few years ago, we kept a steel gong dancing at 110 yds. Same deal.
Max distance for slugs has improved with the advances made in slugs and slug guns. However, it will never be a long range tool as we understand them.