I think the problem is the difference in size of bears. You can find a 100lb bear up to a 400+ pound bear. Smaller ones are basically deer sized game larger ones are smaller than elk or moose so some form of expanding bullet would be required. Personally i think any form of non expanding bullet would be an extremely poor choice other than lead. I shot one with 308 and he dropped on the spot. Autopsy revealed I shot him right thought the spine.
12 g slugs are somewhere around 70 cal don't have one next to me to verify, without any deformation. I've recovered a 300 gr 45 cal xtp from a deer that was expanded to about 75 cal, so from that I conclude the slug is close to max expanded 45 cal before it enters the animal and would be a good choice. In conclusion a hit with a 243 is more effective than the miss with a 12 g. Shot placement will be the deciding factor.
12 g slugs are somewhere around 70 cal don't have one next to me to verify, without any deformation. I've recovered a 300 gr 45 cal xtp from a deer that was expanded to about 75 cal, so from that I conclude the slug is close to max expanded 45 cal before it enters the animal and would be a good choice. In conclusion a hit with a 243 is more effective than the miss with a 12 g. Shot placement will be the deciding factor.