Buckshot should never be used beyond 40 yards max, and they really start losing steam beyond 30 yards. A lot of guys will tell you that they killed deer at 60 or 70 yards, but for every deer killed many more are wounded. One 00 Buckshot pellet at 40 yards has the energy equivalent of a .22 long rifle bullet, make sure that your pattern is still dense enough at that range to hit him with at least half a dozen pellets.