Boddington used his .450-3 1/4" Nitro Express double on this 2007 Botswana tusker. Older cartridges like this with velocity of about 2100 fps work just fine--but the reality is that .416s at about 2400 fps actually penetrate better.
Unlike the other calibers so far discussed, which have quite a bit of versatility, the .45s and larger are very specialized, genuinely suitable and primarily useful only for the largest and most dangerous game. This should make things very simple, but actually it isn't quite that easy because there are a lot of cartridges that use the .458-inch bullet diameter. Bullet weight is important (construction is probably more important), but it's also important to understand that velocity is essential in overcoming resistance. Unfortunately, it is almost impossible to say precisely how much velocity is required to obtain the necessary penetration on large animals. That depends on what the bullet encounters and the exact construction of the bullet.
However, having seen as many failures to penetrate as I wish to see, I'm pretty sure there's a magic number somewhere between 2000 and 2100 fps, at least in the .45s and upwards. Today we have the wonderful luxury not only of better bullets than our forebears, but also an amazing selection of bullets. I am certainly not discounting Sectional Density--the higher the better! However, this is just one factor, and if you can't achieve enough velocity to provide adequate penetration, then the highest SD in the world remains just a number. So, if you want to hunt buffalo or (God help us!) elephant with a .45-70, you need to step down in bullet weight so that you can attain enough velocity to overcome resistance. Thanks to the great modern bullets we have, you can actually do this: There are 400-grain .458 bullets that will absolutely do the job. Perhaps not quite as well as heavier bullets, but well enough.
Okay, that said, the "standard" in .458 remains a 500-grain bullet, SD of .341. Not bad, and certainly good enough. Better is the 550-grain bullet with an SD of .375. Better still is a 600-grain bullet, off the charts with an SD of .409€¦but only if you can push them fast enough. With its limited case capacity, the .458 Winchester Magnum is practically limited to a 500-grain bullet, because you just can't get the heavier bullets to go fast enough. With larger-cased .458-inch cartridges, including the .458 Lott, .450 Dakota, .450 Rigby Rimless, .460 Weatherby Magnum, and so forth, you can go to heavier bullets if you desire. I am sure that penetration on elephant is enhanced. On the other hand, enough is enough, and recoil is also enhanced when bullet weight goes up 10 or 20 percent. The 500-grain .458-inch bullet has been a gold standard for many years, and for those of us who shoot the old .450-3 1/4", this cartridge made its bones (and continues to make them today) with 480-grain bullets.