Worst bruising I ever saw was my dad many years ago firing a 10 gauge single shot goose gun with about a 30 inch barrel. Longest barrel I ever saw on a shotgun. He fired it twice and said that was enough. Gave it back to the guy he got it from. That evening, his shoulder was black in an area about 6 inches wide by about 10 inches high. He was hurting for weeks. Personally, I've never made the attempt. A lesson learned without personal experience.