I won't argue the effectiveness of a 20 gauge shotgun slug, but when I think "back up" I don't think long gun. I think belt gun, one that won't impede my primary mission and has the power to get the job done. If by chance a blackie happens upon you on your setup, chances are it will quickly depart upon your discovery but if not.......there isn't a critter walking this continent that is impervious to a warm 45 Colt load ;-)