Few people realize....
that the ole' 30/30 was actually considered a state-of-the-art, flat-shooting (hey - it could effectively hit targets OVER 100 yards) hard-hitting cartridge when it was intoduced waaaaay back in the century-before-last. LOTS of bear, elk, even cougars, etc. as well as deer where killed with it. Compared to the pistol-sized cartridges most lever guns were chambered for at the time it really was a step or two up. Add the fact that black bears (at least in the southeast) are roughly the size of a large (OK - real large) dog and you get the picture. It is plenty. As stated above, shot-placement is the key no matter what you are shooting.