Well at close range that rifle won't stop a charging bear unless your lucky enough to get a direct heart shot while your heart is pumping and your body is shaking all over the place. Guides that I have been with always carry a 12Ga. slug gun with in case that happens. A slug gun will break a leg if it hits one on a bear a rifle won't, it will just pass right thru. Like he said he said he is new to hunting and was wondering if he should bring his 45/70 with. I figure he is not going to use it to shoot coyotes. So I figured he will use it on a bear if one should happen to surprize him that's all. I'll take the 12 and leave the rifle at home if it were me.
I have to respectfully disagree with you. I'm not saying a 12 gauge isn't adequate for black bear, but a 45-70 is a cannon (buffalo gun). I agree with what you are saying about the panic factor, but any high powered rifle making solid contact with a leg is going to break it. (actually, the panic factor is probably best dealt with with a semi-auto, high capacity large caliber handgun so you can get off multiple shots) Plus, if you do get a good shot to a vital area, the rifle is going to out penetrate the shotgun. My opinion, most rifles and shotguns would be fine for black bears (which I wouldn't worry about that much in the first place -- hunted northern Wisconsin with a single shot .410 for years growing up and then a pump carrying nothing but birdshot).