My goodness there are alot of people on here that think black bears are hard to kill. I wouldn't hesitate to use any "deer caliber" including a .243 on a black bear. Of course I've never killed or even seen a 400-500 pounder but the ones I've seen from PA and Maine sure were not wearing Kevlar. Can't comment on Elk as Ive never hunted them but if I did and only had a .243 I would load it up with a heavy, premium bullet and go get em.