I googled up some info after reading your post and read one article where the author had tested 45/70 loads to a 458w load shooting solids --same gr bullets..

The results they got per the article, showed deeper penetration from the 45/70 than the 458W..not sure if I believe that, but that is what the article stated..

A buddy of mine has had a guide gun in 45-70 for years that he uses to hunt whitetails in the marsh area's...have used it a time or two myself..have to agree that the stepped up loads have some serious kick ...

As to larger game..I have NO doubt the 45-70 would be more than adequate on a buffalo..

Ripp

btw--here is the article mentioned above,,

http://www.garrettcartridges.com/penetration.html