In my experience, nothing makes as good an exit wound as a 12 ga slug. With the heavy bone mass, the layer of fat and the thick fur of a bear, you want a good sized exit wound to give you a good blood trail to follow. Occasionally they will drop in their tracks, but when they don't you want as heavy a blood trail as possible to follow. Slugs are very accurate out to at least 75 yds and the vast majority of bears are shot within 30 yds or less. Wait for a good broadside or quartering away shot and let the slug do its job. Good luck!