I've killed a fair number of bears over the years, mostly in Maine and Canada. I have never considered them any harder to kill then deer of similar body weight.
I did notice, however, that they seem to travel less distance after the shot, if at all, since I started using a 45-70. I tried 425gr hardcast, 400gr JSP and 300gr X bullets and all three put them down rather handily.
Chest shots never stop any of these bullets.
