Quite simple a 350 or even 405gr .458 cast bullet could not come close to a 300gr or 340gr or 350gr .375 bullet.....just not even remotely possible......
Or most anything else, I would have left the .375 part off.......... This OLD bullet tech in 45/70 really is not up to par, it is not capable of buffalo, hippo, or elephant, no argument from me, I concur 100%.
The best bullet of the day, in the early 2000s was a Flat Nose 350 Hornady, it was about as premium as you got..... this bullet was orginally designed for 458 Winchester at those velocities, and Hornady simple gave the bullet a flat nose for lever guns......It would not even expand at all at impacts less than 1650 fps....... current production has changed, and it is softer....... Really none of the common jacked bullets available are capable of anything beyond Zombies and deer....... I really have not kept up with current Premiums, but even most of those in the 350-400 gr weight class would not have enough penetration to be buffalo capable.
OK, we are going to assume that if we buffalo hunt with 45/70, we are going to be using a Lever Gun. I love lever guns, always have, but one must understand the limitations of what we consider traditional lever guns, such as the Winchester M1886, Marlin 1895 and such as that, in larger caliber we have the Winchester/Browning M71s........... The immediate limiting factor is simply Pressure. We do not recommend more than 45000 PSI in the Marlin, and I believe you can push the 1886/M71s to around 50000 PSI. Yes, you can go beyond that, all levers are not created equal, some will go further and not immediately lock up, but at some point you are going to break something with continued prolonged use of over pressure loads.........
This keeps your velocities limited. Simple as that.
The other limiting factor is not very well known. You won't read this in a book or magazine article by the common writers, you won't see this on a TV show by your favorite all knowing celebrity PH Hunter, or what have you. The reason you ask...... They don't know what I am about to tell you, they do not understand or know very little about Bullet Technology and design, in other words, they are ignorant as crap.
We are going to show you one of the factors of Solid Terminal Penetration. This is Factor #4 of 8 total known factors as of today. Factor #4 deals with the forward Nose Projection above the top band of a solid bullet. Flat nose solid bullets, in aqueous medium or animal tissue, do indeed ride inside a Bubble, created by the flat nose of the solid. This bubble extends out beyond the bullet and basically allows the bullet to penetrate deeper because of less resistance.
A lever cartridge must have a "shorter" nose projection, so overall length of the cartridge will work and fit through the magazine and action. The same bullet in a bolt gun can take a "Longer" nose projection above the top band. So what?...... a 400 gr bullet is a 400 gr bullet, right? No, it is not. The Shorter Nose projection means the base of the bullet is longer, more ass behind the nose! The bubble starts to collapse on the base of the bullet, causing drag, slowing it down. The longer nose projection for the bolt gun, or single shot, what have you, pushes the bubble further out, the bullet has less ass, and the bubble collapses behind the rear of the bullet and not one the base. There fore the longer nose projection above the bands will penetrate deeper than the shorter nose projection. You won't find that in a book by your favorite gun writer or PH..........
Don't believe that;
Here are some Properly designed solids in .458 caliber......... You see the two Lever Solids on the left and other bolt gun solids on the right..........Notice the Nose portion of the bullet above the top band.
Now here is a test of the longer nose projection 325 gr CEB Solid
And here is a test in 45/70 of the 325 gr CEB Lever Solid;
Oh, you say, the Longer Nose projection was going faster, and in the case of CEB #13 Solids, yes, velocity is a factor in depth of penetration, and trauma up front, however, even a lever solid at much more velocity does not penetrate any deeper than in the 45/70.......... That bubble is collapsing on the base, slowing it down faster and effecting depth of penetration, regardless of velocity.
OK you say, but what about a heavier bullet say 400 gr .458?
A 400 Lever Solid in 45/70.........
A Lever Solid in 458 B&M........at higher velocity
And a new 400 CEB Solid I just had done with a .600 nose projection........ Now, I had another run done recently, that I have not tested yet, that has a .700 nose projection...... will see if .700 runs deeper than .600.... I don't think it will, but this is why we test.........
Know your cartridge and rifle limitations and capabilities............