The 45-70 was the darling of the buffalo hunters, about the same size as a large bear. I've seen films where they just dropped where they were standing.
My experience is limited to an 1873 Trapdoor, the vernier sight goes to 1200 yds. I've shot it at 1K. Other than being able to take a nap between pulling the trigger and the bullet arriving on target it's pretty impressive.
An ounce is 437.5 gr., OTC cartridges are 405 or 500 gr. In general you're throwing an ounce of lead, that's got to hurt something. The black bear that I shot rolled over and played dead on the spot. I'll swear that the deer was lifted off of it's feet, never did that again.
More info here
http://en.wikipedia.org/wiki/.45-70