There is a little historical disconnect on this topic that is worth exploring.
The old buffalo hunters shot .45-70s and .45-110s at buffalo, and succeeded at very long ranges. That took skill. The bullets didn't move exceptionally fast, and spent a lot of their time subsonic. Errors in range in adjusting their sights could make several inches of drop per yard that they were off at those distances: the greater the distance, the more your bullet is accumulating drop velocity and the steeper the drop angle, so the more sensitive your trajectory is to error. Wind gets in its licks, too. Add to that that you cannot necessarily tell how the wind behaves over the entire flight of your bullet. Yet, when the bullet hit, the terminal ballistics were unarguable. These days, Black Powder Cartridge Rifle competition shooters are shooting .45-70s loaded with heavy bullets (>500gr) with round nose (not flat -- something sometimes called a Creedmore profile) out to 1000 yrds. The game is doping wind, and dealing with very tall vernier sights... and casting their own bullets with as much thermal consistency as they can, and playing with cases, wads, powder tricklers, polishing and uniforming their primer pockets, and all the stuff they can to get the best consistency from their guns. Usually the cases are not crimped; the bullets sit in the end of the cases pretty much finger tight (you can hear the pocket of air pop when they pull the bullet out).
These days, with modern propellants and jacketed bullets, terminal performance is very sensitive to velocity. At higher muzzle velocities, the low BC's of the .458 slugs tend to shed energy quickly. It makes it hard for bullet designers to produce a slug that will perform well at the target at lower velocities and still not fall apart if the target is near the muzzle. The bullet can come apart or fail to penetrate as well as it would have at a slower speed. At the other end, if the bullet doesn't hit hard enough to produce expansion, it will simply pass through without tipover or other effects that help lethality.
As far as trajectory, a .458 win mag can push a 500 gr bullet into a trajectory very similar to a .30-30 win 170gr. The 400 gr bullet in that caliber is much closer to a 7mm waters 120 gr, which is still not as flat as a .30-06 180gr load. The cost of lost velocity in the first several hundred yards that come from pointy bullets is not as great as the impact of initial velocity. Gravity will get in its licks simply because it takes longer to get to 200 yards. Leverfan made the point that the difference is worth maybe 3" out of 20" drop at 300 yrds.
I'll kick in an extra point as well... Ballistic coefficient is roughly proportional to sectional density. There is a contributing form factor -- but the impact of pointiness may not be as significant as ogive and boat-tail. The B.C. divides into a "standard" drag function to get the drag function appropriate for your bullet. There are a number of standard drag functions depending on which bullet profile you're looking at. Some of the earliest were a French military study, Gavre, a German manufacturing company, Krupps, who each published drag functions, Sciacci (flat fire equations) and Mayevski (simple tables for computing trajectories) published analytical techniques and drag tables, followed by Ingall's in the US. This all pretty much came in the 2nd half of the 19th century, with Ingall's work coming out in 1909. Aberdeen produced a number of drag functions for different projectile shapes well into the supersonic domain between 1922 and 1926, labeling these G_1, G_2, etc (G for Gavre in honor of the old French study). The British did parallel work at Hodsock in 1922 (researcher was F. W. Jones). There was later work as well, but for the most part, most of the principles were layed down in the stuff I've cited. As it stands, I have data for 7 different drag functions. The sense is that it isn't quite correct to say that the B.C. depends on speed. Specifically, the functional form of the B.C. is specifically velocity independent. Rather, the speed dependence is supposed to be entirely contained in the drag function (that's the point of deriving B.C.s in the first place). The problem is that there are actually lots of drag functions, and not one of them really does a perfect job capturing the behavior of any particular bullet.
Barnes Originals might be a good compromise (they are set up for .45-70 speeds -- at least, they are listed as .45-70 projectiles, as opposed to being designed for .458 wins, and come in 300gr [457010] and 400 gr [457030] spitzers; the Barnes website claims their Originals don't start to expand until 1900 fps, though), and may behave the way you want them to on smaller game at the ranges you're shooting. The 300 gr bullets will give you more velocity, but have lower BC than the heavier bullets. However, the savings on BC will not make up for the loss of muzzle velocity in the ranges you're shooting. The other facet is whether the spire points might expand better (or worse) than a round nose. That question might give an answer that you'd like to hear.
Actually, I've heard precious little about how the Barnes 457030's perform at .458 win velocities on smaller targets...
Dan
