45-70 vs 458 penetration

[Dav]

Purely from a scientific standpoint:

It’s well recorded that a slower hardcast 430gr .458 bullet such as 1500fps will penetrate much deeper than a 2100fps one, for various factors, bullet deformation and fluid dynamics being the most obvious.

However when considering a hard target such as a buffalo, how deep would the bullet need to penetrate to be considered effective and would a fast bullet penetrate to this depth and at the same time also impact more energy vs a slower bullet that would go much deeper, but with less kinetic impact on the animal ?

If the slow bullet goes more than deep enough, would it still come short of a “proper” shot due to the lower energy dumped into the animal and thus not being effective enough as one would hope when facing a buffalo ?

Which begs the real question; should you try to push your bullet as fast as possible for maximum energy or should you stick to a lower speed for (theoretically) deeper penetration ? The speed being calculated at the target, not at the muzzle.

 

[Ray B]

Similar results: several years ago I tested a bunch of .30" bullets for terminal performance. These were various expanding bullets fired at 30-06 & 300 Wby velocities into water-filled gallon plastic jugs. Penetration for the cup&core bullets at 30-06 velocity ran about 4 jugs. 300 Wby made it into 5. The premium bullets of the time- Nosler Partition and bonded core made it to 7-8 jugs. Now, to your topic- I also fired some lead round balls at considerably slower velocities. they were virtually unstoppable. the stand that I had held 8 jugs, each 6" in diameter, so to pass through 8 the bullet needed to go through 4 feet of water. As you note, the penetration with your bullets was similar to my results. the big difference was in disruption. the jacketed high velocity bullets would completely destroy #1,2 jugs and significantly disrupt #3 and the magnums #4- Water splashes several feet into the air. The slow round lead bullets barely moved the jugs- acting more like an arrow. Pushing through the jugs, making an entry and exit hole the size of the bullet from which water ran out. The shock would have been virtually non-existent, for an animal unless it hit significant bone, the wound may have been fatal but not quick.

 

[BlackRhino]

However when considering a hard target such as a buffalo, how deep would the bullet need to penetrate to be considered effective and would a fast bullet penetrate to this depth and at the same time also impact more energy vs a slower bullet that would go much deeper, but with less kinetic impact on the animal ?

If the slow bullet goes more than deep enough, would it still come short of a “proper” shot due to the lower energy dumped into the animal and thus not being effective enough as one would hope when facing a buffalo ?

For a bullet to be effective, vital organs must be destroyed or at least impaired in their functioning, either directly by the bullet or indirectly by the bullet's shock waves. How deep the penetration must be depends on the question of how quickly the animal should die. Even relatively minor organ damage can lead to the death of the buffalo after a longer period of time. However, if the aim is to kill the animal quickly, then a shot “into the engine room” must hit either the heart and/or the lungs with the bullet and cause sufficient damage. I would consider this to be the minimum penetration required.


Which begs the real question; should you try to push your bullet as fast as possible for maximum energy or should you stick to a lower speed for (theoretically) deeper penetration ? The speed being calculated at the target, not at the muzzle.

If the faster bullet penetrates vital organs, it will – assuming the appropriate bullet type – be more effective due to its higher energy output than the slower bullet, which may penetrate even further into the animal's body.

 

[Dav]

Great answers, thanks for the good explanations.

 

[Choupique]

What youre describing is energy transfer or work, which is a function of the bullets energy and the resistance it encounters. In essence we want to do as much work as possible on the important parts of the animal (structural, nervous, circulatory, respiratory). If you were to walk up to a paralyzed buffalo and slowly shove a sharp pointy half inch rod through it, obviously it would bleed to death or suffocate eventually, but it would take a while. Conversely, hitting him with a blunt .458 tungsten slug at 6,000 fps would obviously have very violent and instantaneous effects.

All that to say, its not really possible to say. Ideally the bullet would impact the animal, break the on-side structure, penetrate to the important parts, halfway fragment, and the other half carry enough juice to break the important structure on the other side. Thats why partitions are so loved, they pretty much do that as reliably as can be expected.

Since we cant realistically expect that it becomes a compromise and a decision about what you want. Do you want to break bones or do you want violent upset and mass destruction of vital tissue? Most buffalo hunters chose the former because while it will kill slower, it generally is more predictable.

The slower load will probably penetrate better in tissue. Will it penetrate bone better? How do we make it fragment in the lungs, which are 50% air? All that to say its really difficult to make a buffalo bullet be perfect. Theres too much variation in density and resistance in a given cross-section of the animal and it changed wildly with the angle.

 

[Rafiki]

Garett Cartridge has some interesting info on this subject on their website.

 

[5shot]

The Linebaugh Pentetration tests used bovine bones and wet newspaper. Hard cast 45-70 is a powerful tool.