I feel exactly the same way you do with regard to the 45/70, but let's not get too carried away with the bow thing either. You may have vastly more experience than me hunting buffalo but I find having that PH along a mildly useful addition to the effort. I have killed dozens of deer with a bow and have enormous respect for their inherent abilities, but I have little expectation it would do anything at all to an in bound bull. Something that can happen no matter how carefully one places the first shot. But with respect to your basic point, I absolutely agree. Penetration is everything. My personal comparison is that for buffalo I would rather use a .30 (200 gr) or .333 (250 gr) solid than any 45/70 load (or period .450/500 or .500 BP Express). The BP era .45's have all the deficiencies of greater frontal area with few of the advantages. The .318 WR Express was a well respected buffalo round in its solid 250 gr form. That was at a time when a host of BP era, large caliber martini, farquharson, and break-action rifles were gathering dust in closets. Can a 45/70 kill a buffalo? Sure. Just remember, when you pull that trigger, you have just assumed responsibility for not just yourself but also everyone in that party. I think there is an ethical responsibility to make that first shot as accurate and lethal as humanly possible. There are a host of good DG calibers, many with historic pedigrees if that is important, to accomplish that task.