Ya, I've heard too that the 375 H&H was the caliber most prefered by the old hide hunters. We were on a hunt one year, when a hunter in another party shot a large cow three times through the front end at 65 yards. He was using a Remington 700 in 7MM mag. After the third shot, she was still standing. One of the hunters in our group shot her one time with a .50-70 rolling block sporter and knocked her off her feet. A well placed shot and a slow, heavy bullet are far more effective on buffalo. It's like getting hit with a soft ball at 400 miles an hour. It's always best when the bullet energy is used up inside an animal. Even a through and through shot will work fine if it's in the right spot. Many hunters shoot a buffalo too high up and it does very little damage. Buffalo are built different than most large game animals. All the vitals are low, between the front legs and the chest. The .45-75 WCF is an exceptional cartridge, when loaded with black powder. You could certainly hunt any big game in North America with this cartridge, as long as you keep in mind the effective range. I've shot 30" steel plate at 600 yards with one of my original rifles, using the special order long range sights that came on the gun from the factory. Fifteen hits out of twenty shots wasn't a problem. But, I would never hunt at anything close to that range. In my opinion, the best effective range for hunting small and medium size game with the .45-75 WCF, would be 200 yards max.
Adios,
Buck