At least as far as the .45-70 is concerned with whitetailed deer, there's practically nothing I could shoot that wouldn't be effective.
Agree. In fact, there's practcally nothing you could shoot out of the .45-70 that wouldn't be effective on any and all north american big game.
I used to handload a lot of 45-70 but I haven't for a long time. However, I just aquired an 1886 so I intend to begin handloading 45-70 again soon.
I only like loading jacketed bullets in this cartridge. I'll occassionally shoot cast factory loads. But I consider handloading cast bullets to be unnecessarily messy and I don't like playing with gas checks.
For a long time, I favored 300 grain bullets over 400 grain(ish) bullets because they can be fired at higher velocities with flatter trajectories. If you zero and shoot your rifle at 100 yards there's not too great a difference between trajectories to cause a problem. But if you zero at 100 yards then shoot at 150 or 200 the difference in drop becomes significant. Alternatively, if you zero them both for 200 yards the 400 grain bullet is unacceptably high midrange.
Then I discovered the Hornady 350 grain round nose. It's the best of both worlds. It shoots significaltly faster and flatter than the 400(ish) grain flatnose. It can't be shot as fast as a 300 grain bullet but the round nose helps it keep velocity downrange. So, it ends up shooting about as flat as the 300 grainers.
I refrain from shooting FTX polymer (gummy) tip bullets. They have an aerodynamic advantage but pull the tip out and you'll see they're really just a massive, quick expanding hollowpoint. I have no plans to handload any of those.
Bottom line, I choose the 350gr roundnose over all else.