The following is based on over 25 years making a living as a licensed guide in Alaska and as a professional hunter in Africa. Between clients shooting game and cull hunts I have personally seen over 7,000 big game (250 lbs or more) animals die from gunshots. I have formed my opinions on terminal ballistics from this experience
The Biggest Myth that I hear is faster projectiles (Velocity) kills better than slow ones. As long as the projectile stays above supersonic it will kill big game effectively with a properly constructed bullet.
Second Biggest Myth is that more foot-pounds of energy = better killing/stopping power. Foot pounds of energy is just a mathematical figure and has very little to do with stopping or killing power.
Bullet diameters and bullet design has more to do with killing/stopping power than speed. The best hunting bullets are the ones that perform over the widest range of velocities, leave the largest permanent wound channel, will not brake apart when they hit heavy bone and will consistently exit the animal on a broadside shot.
On big game larger heavier bullets kill better than smaller faster ones.
At close range, a flat-nosed 540 grain bullet fired from a .45-70 at 1,550 FPS has far more stopping/ killing power than any of the .30, .338 or .375 magnum. But at the same time a projectile with a flat trajectories is easer to make good hits at longer ranges than the slow moving 540 grain slug from the .45-70.
Faster bullets do give better trajectory and extend the range we can make good hits at. A good hit with a smaller caliber is always better than a poor hit with a larger caliber
For consistent kills on big game, the larger caliber bullet the better and the heaviest bullet for a given caliber will have the best knock down power.
For the first third of my guiding career I thought that perfect bullet performance was to find the bullet in the hide on the far side. That way all the energy has been absorb by the animal. . Over the years I changed my opinion for the following reasons
1. Exit wounds leave a lot better blood trail.
2. Granted, most shots taken are broadside but if a bullet cannot punch through an animal with a broadside shot and exit the animal then it does not have enough penetration to go end to end on an animal. You do not always get broadside shots while hunting and rarely get a broadside shot on a charging or fleeing critter.
3. I want my bullets to be able to break heavy bone and continue to penetrate deeply afterwards.
4. I no longer believe that it is the energy that kills but the size of the wound channel.
There is no best bullet (or caliber) for hunting. Even the best designed bullet will occasionally fail to do the job it is intended to do, Poorly made or poorly designed bullets will conversely give spectacular killing results from time to time.
It is the trend that is important in bullets. From my point of view a half dozen cases of good or poor bullet performance is not much of a trend. Around a hundred is what I want to see. I once witnessed a Kudu (elk-sized African Antelope) shot at 40 yards with a .416 using a 400 grain swift a frame. The well placed bullet hit the Kudu broadside. It ran off and we had to track it for two days. The shot placement was good the cartridge and bullet excellent but it still failed. The same client shot a cape buff with all the same conditions/shot placement and the buff fell over dead with the one shot. The bullet exited after breaking the shoulder. Neither of these isolated cases proves anything.
All bullets are a compromise: No Spire point bullet will ever have as good of terminal ballistics as a flat meplat bullet and no flat nosed bullet has as good of arrow dynamics as a spire point.
The best killing and the best knock down bullets have a large flat nose with a sharp edge (large meplat). Elmer Keith and J.D. Jones have both promoted this concept with handgun bullets. The best example for a rifle is Randy Garrett’s 540 Grain .45-caliber bullet loaded in his .45-70+P ammo. Up close this round has more stopping power than conventional hunting bullets shot from the .458 Winchester Magnum. Now the Garrett 540 grain bullet is fantastic at close range but not what I would recommend for long range situations and it will not feed reliably in most bolt actions. Check out the Garrett ammo web site, read the data how his .45-70 ammo out-penetrates the .458 Winchester.
I have had clients make clean kills on big game using every thing from .223 to .50 but the best consistency for clean kills was with large [diameter] heavy projectiles. Most of my career I used one of three calibers: 308 Winchester, .375 H&H and .470 [Nitro Express]. For cull hunts and wolf hunting I used .308. Every 7.62mm diameter bullet can kill. Military ball [aka full metal jacket (FMJ)] was supplied for most cull hunts. Ball is the worst, but it works in a pinch. The best killing bullets I found in .308 caliber was the [Nosler] Fail Safe and Barnes X bullet. There other very good bullets but the Barnes and Fail Safe stand out in my mind.
For guiding in Alaska and for African plains game I used 375 H&H. The .375 diameter 300-grain Sierra is a wonderfully accurate bullet but at close range it comes apart and sheds it’s jacket fairly often so I do not recommend it for big Bear, Cape Buffalo, Hippo or Rhino. The Barnes, Nosler partition, Swift A-frame and Trophy Bonded are all wonderful .375 projectiles and usually hold together at close range. I would use any of the 4 and pick the one that shoots the best in your particular rifle.
I am not a fan of the .375 for Cape Buffalo, Hippo or Rhino. The .416 or .458 with the Barnes X or trophy bonded seems to be the most consistent killer at all ranges on the thick skinned game. A good .470 or .500 double rifle is best for the big stuff but not many can justify spending $10,000+ for a double rifle and at least $10 per round of ammo.
Enough of my rambling this is the bottom line. Shot Placement is the Single Most Important Factor.
For big game use the largest caliber with the heaviest bullet that you can shoot accurately. I would rather a client show up on a Grizzly hunt with a 30-06 that he can shoot well than a have him bring a .375 that he does not shoot accurately. Use premium hunting bullets–not target bullets–for big game. – Old Dog in Alaska