The .45-70 is a dandy old cartridge. Handloaders can really juice it up in modern rifles like the Marlin 1895. Factory ammo is loaded down considerably to avoid blowing up the older guns that can't take the pressure.
If you do handload for the .45-70 be sure to read all the precautions both in the loading manuals and from your weapon's manufacturer.
My last black bear was taken with a Remington 300 gr and at about 50 yds, looked like it drove the bugger about 3 ft sideways, got up, tried to run and rolled down the hillside DOA.