Bullets for Big Game

Measuring what's Missing

In the article on rifle cartridge selection, the practicality of killing big game animals was examined. But, as simple as putting a good bullet in the right spot might be, hunters demand a more clinical explanation – they want killing ability quantified with, velocity, energy, penetration, bullet weight, and bullet upset or expansion as some like to call it. Though I’m sure definitive quantification is impossible, I do believe there’s some reasonable assumptions that can be made. I also think most hunters are making these assumptions on the wrong measures.

Dead is dead, and one bullet cannot make an animal deader than another. But, given the same shot placement, some bullets can make animals bleed more than others. And blood loss is the most reliable factor a hunter can count on when it comes to ethical shot placement and putting animals down fast. The question is, how do we optimize blood loss?

Velocity

The speed at which a bullet impacts an animal matters. If you’ve done much prairie dog shooting you know this. Whack a prairie rat at 50 yards with a 223 Remington and he will erupt. Shoot another at 400 yards and there’s a lot less red mist. This is partly because the amount of bullet upset experienced is driven by velocity, and partly because when bullets impact a living creature they create a splash, much like the difference between dropping or throwing a rock in a pond – the faster the bullet impacts, the bigger the splash.

Also, and this is very critical, all bullets have a velocity threshold. All bullets need to impact at a minimum velocity for there to be any bullet upset at all. The tougher the bullet is made, the more velocity it needs. Though this minimum impact velocity will be different for all bullets – especially for bullets specifically engineered for low velocity rifle cartridges – as a general guide you can use the following guide for bullets intended for high velocity rifle cartridges:

Copper/mono-metal bullets: 1800 to 2000 fps

Bonded bullets: 1600 to 1800 fps

Conventional lead-core bullets: 1400 to 1600 fps.

• All bullets designed to upset on impact have a minimum velocity threshold that must be achieved for deformation to occur.

Energy

Kinetic energy is often offered as a measure of a bullet or even a cartridge’s ability to kill an animal. The general assumption is that more energy equates to a faster kill or more tissue damage. All things being equal there is some truth to this, but when comparing different bullets, all things are never equal. The amount of energy is not nearly as important as the way in which that energy is put to work.

Here's a perfect example. A solid non-deforming bullet like is often used for dangerous game will have the same energy as a deforming bullet of the same caliber, weight, and velocity. However, the way these two bullets damage tissues are radically different. One bullet will poke a very deep and small diameter hole while the other bullet will create a massive wound cavity much larger than bullet diameter but not as deep as the solid. It’s not about energy, it’s about work.

Penetration

This is the easiest element of terminal performance to quantify. You simply must have enough penetration to completely pierce the vitals. The complicated part about penetration is that enough will vary with shot angle and animal size, and if you want the bullet to exit. Some like a bullet to exit and while a bullet exiting has nothing to do with its ability to kill, it can make following a blood trail easier. The bottom line with penetration is that, once you achieve enough no more is necessary, and enough will vary from situation to situation.

• Bullet penetration is often measured in 10% ordnance gelatin, but it rarely if ever correlates to actual penetration depths in animals.

Bullet Weight

In the arena of terminal performance there’s a lot of credence given to bullet weight. Bullet weight is part of terminal performance, but no more – and maybe not as important – as everything else. One notion is that heavier bullets are better. This is partly a holdover from back in the day when velocities climbed above the levels that the bullets of that time could withstand. By going to a heavier bullet hunters found better terminal performance because velocity dropped to levels the bullets were built for, and the bullets did not come apart on the hide of a mud covered moose.

The bullets of today are much better at withstanding high impact velocities, but many still believe if you’re after a bigger animal you need a heavier bullet. For example, with .30-claiber bullets many think a 150-grain bullet is fine for deer, but you’ll need a 180-grain bullet for elk. Let’s look at a test involving two bullets of identical construction and see what the actual terminal performance difference is. I fired 150- and 180-grain Sierra ProHunter SPT bullets into a proprietary wax testing medium at practical 100 yard impact velocities. (Apparently Sierra no longer makes a 180-grain SPT ProHunter bullet.) The results might surprise you.

• Sierra ProHunter 180-grain (left), Sierra ProHunter 150-grain (right)

The 20% weight advantage of the 180-grain bullet allowed it to penetrate only 0.75-inch (5%) deeper. However, the volume of the wound cavity created by the 150-grain bullet – partially due to its higher velocity – was 20% larger. The weight of the recovered bullet is often touted as an indicator of the bullet’s ability to kill or damage tissue. In this case, the 150-grain bullet only retained 84% of its weight, while the 180-grain bullet retained 94%.

This misconception about bullet weight is perfectly illustrated by a question the great African professional hunter and gun writer Finn Aagaard once asked, “Given sufficient penetration, what does any additional bullet weight add to killing power? Nothing, absolutely nothing.”

Bullet Upset

Various bullet testing mediums are used to help with the design and evaluation of terminal performance. 10% ordnance gelatin is generally considered the standard, but it’s nothing more than water – 90% water – held together in a solid block. Clear Ballistics is a great medium for the home ballistician, but mostly only allows for the measure of penetration. Much like ordnance gelatin the cracks and fissures seen in the blocks, while visually stunning, are not quantifiable. The beauty of ballistic wax like we developed for the now discontinued Bullet Test Tube is that it allows for the exact volumetric measurement of the wound cavity the bullet creates. This allows you to quantify the potential for tissue damage, but to also see how the material the bullet shed contributes to wounding.

In the Sierra ProHunter example, the 150-grain bullet shed 24 grains of weight in the form of fractured lead. That lead that was dispersed with velocity inside the ballistic wax, and combined with the 150-grain bullet’s higher velocity it’s what created the 20% larger wound cavity. The 180-grain bullet only shed 10-grains of lead. Most would think it a better killing bullet but one way of looking at it is that the bullet did not shed enough material to do the work necessary to damage as much tissue.

• Nosler Ballistic Tip, Nosler AccuBond, Nosler Partition, Hornady InterBond, Winchester FailSafe, Barnes TSX (left to right)

Maybe a better example of how the material a bullet sheds or how bullet upset contributes to wounding is another test I conducted in ballistic wax using six different 0.308-caliber bullets. These 150-grain bullets were fired at near identical velocities and are listed in the table from the largest to smallest in terms of wound cavity volume. As you can see, the wound cavity size has a correlation to the amount of material the bullet shed, because this shedding of material contributes to wounding. There were however two — now extinct — exceptions.

The first exception was the now defunct Hornady Interbond. This bonded bullet held together well and created the largest wound cavity. However, because it upset with such a wide frontal diameter — which added to the wound cavity size and splash — it’s penetration was well below average or what might be considered “sufficient.” The other exception was the Winchester Fail Safe. Some hunters like Dave Petzal liked it, but it could be considered a Failure because it’s no longer offered either. This bullet shed a good bit of weight but the petals/pieces it shed just broke away and were left behind the bullet, they did not contribute to wounding. Because of its minimal frontal diameter, it penetrated deep but its wound cavity size was well below the average.

Copper & Lead

One company that manufactures all-copper mono-metal bullets liked to tout the fact that their bullets killed quicker while damaging less meat. I’m sorry but this is an impossibility. Short of structural or neurological damage, animals fall down and don’t get up due to blood loss, and blood loss directly correlates to tissue damage. The more tissue that’s damaged, the more hemorrhaging occurs. Mono-metal bullets penetrate very well because they retain all their weight. Lead core bullets damage more tissue because they either upset with a wind frontal dimeter – like the Hornady InterBond – or because the material/lead they shed does the dirty work.

Granted, if you shoot a whitetail deer through the lungs with any of the six bullets they will die! However, it is a fact that the bullets that create the largest wound cavities will make the deer bleed more. And, deer that bleed more, fall down sooner. Of course, the incapacitation of a big game animal is not a matter of numbers, it’s all about biology and the animal’s level of alertness and adrenalin all contribute to collapse as swell. But I can say that after having witnessed hundreds of big game animals shot with many different types of bullets, it’s the bullets capable of creating the larger wound cavities that usually put animals down the quickest.

I’m not going to bother with all that fast expansion crap. All bullets begin to deform on or just after impact and they complete the process in about the same amount of time. If you want to dig into this myth deeper, READ THIS. I’m also not going to get into the lead particles in meat discussion. If it bothers you to shoot an animal you intend to eat with a lead bullet, then don’t do it.

• Notice the lead particles in the Partition’s and AccuBond’s wound cavities that were dispersed under velocity. This lead dispersion amplifies wounding. (Images not to scale.)

This all takes us back more than 75 years ago when John Nosler created his Partition bullet because the bullets at the time were too lightly constructed to deliver Aagaard’s “sufficient” penetration. The front lead core of the Partition sheds itself and is blasted into the tissue to create a massive wound cavity. But then the rear core, which is protected by the bullet’s partition, continues to penetrate. The Nosler AccuBond is simply a bonded bullet that’s designed to perform very similarly.

Until recently, this is terminal performance that was unattainable with mono-metal bullets. This is one reason mono-metal bullet manufacturers and users often suggest stepping down to a lighter weight bullet. This gives the bullet a higher velocity without sacrificing penetration, and the additional velocity creates a bigger splash inside the animal. For example, a 130-grain Barnes TSX impacting at about 2900 fps will create a wound cavity about the same size, with about the same depth of penetration, as a 150-grain Nosler AccuBond. It does this with velocity and frontal diameter — a splash — as opposed to lead dispersion.

The Controlled Chaos

Almost 20 years ago I helped a friend design and test a bullet for a rifle cartridge he’d created. Borrowing on the design of the French made GPA bullet, this new bullet was also similar to a Barnes Triple Shock. The difference was that the petals were designed to break away instantly. He teamed with Lehigh Defense to create a very wicked bullet which I’ve also tested in Africa on animals as large as eland and buffalo. This ultimately became what’s now known as the Controlled Chaos.

The Controlled Chaos sort of bridges the gap between lead core and mono-metal bullets; it gives both high energy transfer through material shedding and provides deep penetration. Unlike the all-copper Barnes Triple Shock, which forms petals that the bullet retains; the Controlled Chaos bullet erupts creating shrapnel. This shrapnel is not left in pieces behind the trial of the bullet, the eruption comes almost instantly, and all this shed material retains velocity and travels forward, radiating out from the bullet’s path much like the lead particles of a Nosler Partition. This leaves the bullet’s shank to continue to penetrate, again, much like the Partition.

• Lehigh Defense Tipped Controlled Chaos bullet upset at (left to right) 1,900 fps, 2,400 fps, and 2,700 fps.

Lehigh Defense is now developing a tipped version of this bullet and unlike lead core bullets that will vary in upset diameter and the amount of material they shed based on impact velocity, this all-copper Lehigh Defense bullet seems to be velocity blind. By that I mean that it comes apart about the same at 100 yards as it will at 300 yards. I’ve yet to test this bullet on a big game animal but I’m slated to do that in Texas very soon and in Africa next spring. I’ll let you know how it works.

Measuring the Missing

I believe that much like with rifle cartridge selection, bullet selection – at least with most modern big game bullets – is not that critical; most will get the job done. Sure, you have to be careful with lightly constructed bullets at ultra-high impact velocities, just as you need to be careful with very tough bullets at low impact velocities. Just like with rifle cartridge selection, avoid the extremes.

But I also firmly believe that bullet manufactures – and gun writers with limited big game hunting and autopsy experience – have convinced most hunters that a tough bullet and high weight retention are best. I think the perfect big game bullet would achieve “sufficient penetration” and retain less than 10% of its weight. That would allow the 90% of the bullet to do the work of maximizing tissue destruction. Of course, the problem with this concept is that sufficient penetration varies due to animal size and shot angle.

• Some of this bullet is missing and that missing material was put to work to damage tissue and make the animal — in this case a moose — bleed.

Because of these variances we must make bullets that will always retain a good portion of their weight to achieve that magical sufficient penetration regardless of shot angle and animal size. The Nosler Partition and AccuBond, as well as the Lehigh Defense Controlled Chaos bullets, are about as close to this ideal as has yet to be engineered. Bullets that retain all their weight are truly tough as hell, but every grain of weight they retain is a grain of weight that was not put to work to make the animal bleed. What me might need to be measuring is what’s missing as opposed to what’s left over.