After more than 50 years of guiding and hunting, much of which involved both black and grizzly bears, my experience compels me to post as the odd man out in this discussion. While the 45-70 is a great hunting round it is not nearly the stopping cartridge many think. It has great penetration, but only marginal success as a quick killer.
Bears are not difficult to kill in usual hunting situations, no more so than a deer. If I am correct in understanding this thread, the concern here is not primarily defence, but that of unexpected defence that might occur during an ordinary hunting effort. This, in particular against a bear at close range or one in a charge. I have been involved in both on several occasions, and know others who have as well.
If I had my choice I would want nothing other than the rifle I handled and shot the best. Unless I had many, many, hundreds of rounds of offhand practice with relatively hard recoiling 45-70, it would be far from my first choice. Believe me when I tell you that the excitement of having a bear fall close enough to your feet that you can touch his open eye to check for reflex will be more than enough for that day. The closest I ever had was with my "little" Husqvarna 270 that I had used for many years, shot several thousand times at the range, hunting groundhogs and big game.
My friend Jared Wilkinson did exactly the same while hunting grouse with a 20 gauge single shot. The bear fell less than a single lone pace away.
Again, if I had my choice I would want nothing other than the rifle I handled and shot the best. No flies on the 45-70 except perhaps for recoil and limited range, but for an everyday hunting outfit, where I need to do more than worry about an unexpected bear encounter, your 30-06 would be my choice.
Best,
Ted
