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How Bullets Work
The wound cavity produced by a bullet is what kills deer. Wound cavities come in two types: permanent and temporary. A permanent wound cavity, crush cavity or wound channel is the actual tissue that the bullet destroys as it passes through the animal. A temporary or stretch cavity is caused by the hydrostatic displacement of tissue during expansion and penetration. This cavity is not as destructive, but can bust blood vessels and tear organs. Generally, stretch cavities are more violent with lightly constructed bullets and high velocities.
Bullets or wound cavities kill whitetails in several ways. Blood loss due to the damage caused by permanent or stretch cavities can ultimately lead to the deer’s death if the right blood vessels or organs are damaged. Strangulation or suffocation can also be a cause of death when both lungs are extensively injured or become filled with blood.
Lungs that have collapsed or are full of blood will not allow a deer to stay on its feet long. Structural damage caused by a bullet’s permanent cavity can put a deer on the ground or at least slow them, but structural damage alone does not kill. A whitetail can go a long way with damage to more than one shoulder or leg. And while a bullet that penetrates the spinal column might drop a deer instantly, in many cases a coupe de grâce is required to prevent suffering.
Photo: All of these bullets were recovered from white-tailed deer. (Left to right): 100-grain Hornady .257 Interlock; 180-grain Remington Core-Lokt SP; 170-grain 8mm Remington Core-Lokt; 200-grain .35-caliber Federal Hi-Shock SP.
Finally, deer can also be put down with a shock to the nervous system. Bullets that strike in or near high nerve concentrations can create massive shock via the crush or stretch cavities. This can drop an animal like lightning. If the bullet also manages to hit the spine or cause massive damage to the lungs or heart, the deer might not take another step.
Penetration
You do not have to shoot completely through a whitetail to kill it. But sometimes you might have to shoot though a whole lot of deer to get the bullet into a place that will kill it. To be sure, in order to inflict a substantial amount of damage on a whitetail, the bullet needs to penetrate deep enough. Some will argue the bullet should remain in the deer, thus transferring all of its energy.
But in reality, a bullet does not possess a great deal of energy, certainly not enough to knock a deer down. The benefits of a “for sure” exit wound far outweigh any imagined knockdown power a bullet might possess. Those one-shot knockdowns you witness in the field are not a result of the animal being slammed to the ground by the bullet’s impact. They come from immediate failure of the deer’s support structure or nervous system.
Photo: Better expansion and weight retention would be hard to find. This Naturalis bullet from Lapua for the 9.3x62 is picture perfect. The bullet was recovered from dry paper.
Blood trails are always better when they come from two holes instead of one. And a bullet that has enough power to reach the vitals on both sides, regardless of the shot angle, gives us confidence. If your particular gun/bullet combination is only capable of putting a bullet through the lungs to stop under the hide on the far side, what happens if your aim is a bit off and the bullet strikes a shoulder on the way in? It might never reach the heart or both lungs. Complete penetration is best.
Expansion, Weight and Velocity
The more a bullet expands, the more resistance it meets during penetration, and the larger crush cavity it leaves behind. However, a bullet can overexpand or even come apart after penetration, leaving a violent but shallow crush and stretch cavity.
Most hunting bullets reach full expansion by the time they have traveled 8 inches inside a deer. I have verified this by testing bullets in various mediums, examining harvested deer and talking with bullet technicians from Nosler, Federal and Winchester. Expansion is driven by velocity. The higher the velocity at impact, the more a bullet will expand. Impact velocity dictates expansion, not the depth a bullet travels within the animal.
Some claim that premium bullets are constructed too tough to reliably expand in deer. That’s simply not true. With a premium bullet, expansion is slowed, and the hydrostatic stretch cavity is not as pronounced as with fast-expanding bullets. Premium bullets do create wide, deep crush cavities due to their higher retained weight and good expansion.
Retained weight gets a lot of attention, but the concept can be misleading. Bullets are not constructed of valuable metals, and you are not going to reuse them. So why do we make a big deal about high weight retention when ideally you should be shooting through deer and unable to recover bullets? Partly because a bullet that retains more weight appears to be tougher made, and “tough” sounds good. The truth is that most bullets considered suitable for deer will retain around 50 percent or more of their initial weight as long as they are used at the velocity levels for which they were designed.
Photo: The Nosler Partition loses its front core during expansion, creating a massive wound channel. The jacket and rear continue to penetrate after the bullet upsets.
To fully understand expansion, you have to realize that bullets are designed to open or expand within a certain velocity range. Generally speaking, standard bullets like Winchester Power Points and Silvertips, Remington Core-Lokts, Speer Hot Core, Hornady Interlock and even Nosler Ballistic Tips intended for modern cartridges, are engineered to perform best at impact velocities between 1,800 and 2,800 fps. Bullets designed for cartridges that operate at slower velocities, like the .30-30 Winchester, .35 Remington and .45-70, will expand at velocities as low as 1,500 fps and work well up to about 2,500 fps.
Premium bullets like Nosler Partitions, Barnes X, Speer Grand Slams and Trophy Bonded Bear Claws offer high weight retention, which in theory should increase penetration because a heavier bullet is harder to stop.
It is important to apply common sense when using any bullet. You would not want to use a .30-30 bullet in a .300 Ultra Mag. It would likely come to pieces just under the hide of a whitetail at such high velocity. And a bullet designed for the .300 Winchester Magnum might not open up at .30-30 velocities. But, at 100 yards, the .30-30 will kill a deer just as well as the .300 Ultra Mag with the proper bullet. The key is to find a balance between expansion, weight retention and velocity. John Nosler did this many years ago when he created the Nosler Partition.
Many hunters do not understand premium bullets. A friend who has hunted all over the world told a story about a Nosler Partition that, in his words, failed. He had shot a sheep at an outrageous range. He recovered the bullet and found that it had lost its front core. He swore that was the last Partition he would use.
Nosler Partitions are designed to work under heavy stress. By losing the front core during expansion, they create a massive wound channel. Then, the remaining jacket and intact rear travel through the animal, creating additional destruction. This front core loss is the Partition’s way of dealing with difficult penetration and high velocity – kind of like a built-in safety mechanism.
Partitions had served my friend well for many years until he hit a critter that was so far away, velocity was insufficient to poke the bullet out the other side of the beast.
You can test bullets in various mediums to find out how they will perform in that material. It’s a good way compare different bullets. I have done just that, using sand, dirt, and wet and dry paper. It is an interesting but tedious task that is difficult to pull off at public shooting ranges. It is much easier to facilitate if, like mine, your range is behind your house. Still, the only true test of a deer bullet is a deer.
In the real world, picking the right bullet for whitetail hunting is not that complicated; deer are not that tough. There are some rules of thumb that you can go by to keep you out of deer bullet trouble:
• At impact velocities over 3,000 fps, always use premium bullets.
• For impact velocities less than 2,800 fps, standard bullets work just fine.
• With borderline impact velocities between 2,800 and 3,000 fps, standard bullets that are heavy for the caliber, like a 180-grain .30 caliber or a 150-grain .277 caliber, can add extra insurance.
• If you are using a bullet that is light for the caliber or bullets under 100 grains, a premium bullet is never a bad choice.
Of course, you could take the advice of good friend and custom rifle builder Charlie Sisk: “Load a Nosler Partition, shut up and go hunting.” That philosophy does not offer much variety, but it’s sure hard to argue with.
– Richard A. Mann II