I wouldn't go under a 30 cal for a clean kill imho. I grew up around black bears. 99% of time they are skittish, and afraid of humans. Obviously you injure one, or get between a mother and it's babies it's a whole other story. The meat is garbage, and you will probably only want sausage out of it, so this is most likely a sport kill. Most of the guys I grew up with that hunted them used 308's or 30-06. Hide isn't crazy tough, but I still think a 223 is a bit underpowered for them.