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Hunters, unlike anglers, cannot practice catch and release while enjoying their preferred outdoor activity. While not every hunt results in a kill, killing is the goal of the hunt. Intent to kill an animal is what differentiates a hunt from an armed hike. As ethical hunters, we have a duty to minimize the suffering of our quarry by doing everything in our power to ensure a clean, quick kill. One of the most important ways we can increase the chances of a clean kill is by using a firearm chambered in a cartridge of sufficient power for the game being hunted. Here are some things to consider when deciding on a big game round.
The science of terminal ballistics, or what happens when a bullet hits something, is a complex blend of physics and physiology that cannot be fully explored in a few paragraphs. For an in-depth discussion of this fascinating science, this site is highly recommended. Read on for an abbreviated explanation. In order for a bullet to quickly and humanely kill a large game animal, it must destroy sufficient vital tissue to cause death by rapid exsanguination (bleeding) or by causing severe trauma to the central nervous system (brain and spinal cord). Since the central nervous system of even the largest big game animals is a comparatively small target that can be difficult to hit under field conditions, most hunters will aim for the large, capillary rich vital organs in the thoracic cavity (heart, lungs and liver). High velocity bullets such as those fired from common big game rifles impart damage to such vital tissues via three primary mechanisms: penetration, cavitation, and fragmentation. Penetration is the depth to which a bullet pierces tissue. Cavitation is a space in tissue created by the bullet. A wound cavity created by a rifle bullet typically consists of two sub-types; a permanent cavity created by the crushing and tearing of tissue as a bullet passes though, and a temporary stretch cavity caused by the energy of the bullet being transferred to tissue via hydraulic action. Some schools of ballistic thought assert that a large temporary cavity can result in a large permanent cavity as vital tissue stretches to its tearing point under stress. The slow motion video below demonstrates the cavitation that occurs as a bullet passes through a block of ballistic gelatin, which is designed to mimic the muscle tissue of mammals. Fragmentation occurs as a bullet breaks apart into smaller projectiles as it travels through tissue. The bullet fragments may take paths that angle away from the path of the bullet and lacerate additional tissue as they do so.
Generally speaking, as bullet impact velocity and bullet mass (aka energy) increases, so too does the wounding potential of the bullet in question. An increase in the frontal diameter of a bullet will also increase tissue damage. To this demonstrated in action, compare these two slow motion videos of bullets passing through gel blocks. The above video demonstrates the effect a .224” diameter, 40 grain projectile impacting at a velocity of 1854 feet per second (fps) has on a mammalian tissue analogue vs. the effect a .308”, 160 grain projectile impacting at a velocity of 2,399 fps has on the same test medium in the video below. The larger, heavier, faster bullet created a far larger cavity (both temporary and permanent) and offered far greater penetration than its more diminutive cousin. The amount of damage done by this bullet is what a humane, ethical hunter should strive for when selecting a big game cartridge.
If increases in bullet mass and velocity translate to increased killing ability, then why don’t we all choose big game rounds that sport the biggest, fastest, bullets allowable by law? The answer, of course, is recoil. Newton’s third law is inescapable and every increase in bullet mass and velocity translate to an increase in the amount of recoil absorbed by the hunter’s shoulder. High levels of recoil can cause discomfort to outright pain, which can result in a flinch, which in turn can result in poor shooting. Most hunters will find it easier to consistently hit their targets when shooting rounds that don’t beat the living daylights out of them with each pull of the trigger. Balancing recoil with terminal performance is a vital consideration when choosing a big game round.
While bullet mass, velocity, and diameter are all highly important factors to consider when selecting a big bullet, the composition of the bullet is another important and often overlooked consideration. If a bullet is designed so as to not expand appreciably or at all (military full metal jackets come to mind) the bullet stands a chance of carving a very narrow wound through an animal that may not inflict sufficient organ trauma to ensure a quick death. Such a wound, though ultimately fatal, may allow the animal time to escape before expiring. Above: Full metal jacket bullets are not typically considered an ethical option for big game hunting. On the other end of the spectrum, bullets that are too fragile (prone to breaking apart) stand a chance of completely fragmenting upon impact, which can result in a wide, shallow, wound that does not penetrate to a sufficient depth. Once again, such a wound may be ultimately fatal, but not quickly enough to be considered humane. In general, the best big game bullets are those that provide a balance of expansion and penetration. Bullets that flatten and expand into a textbook mushroom shape upon impact while maintaining enough integrity to sufficiently penetrate to the vitals are ideal. Examples of such expanding bullets include jacketed soft points (a bullet with a lead core, copper jacket and an exposed lead tip) partitioned bullets (bullets where the expanding front section of the bullet is separated from the rear section by a thick layer of copper) and pre-segmented, all copper, monolithic bullets such as the various incarnations of the Barnes X bullet. Above: A monolithic bullet before and after expansion Be aware that expanding bullets work best within an ideal impact velocity window; the bullet that expands perfectly at an impact velocity of 2,500 fps may not expand appreciably at a greater distance when the impact velocity drops to 1,500 fps. One exception to this rule against non-expanding bullets occurs when large diameter (.375” and larger) bullets of a hard alloy composition are employed. This is especially true if said bullets have wide, flat, tips (or meplats). The sheer size and mass of such bullets coupled with their flat, tissue disrupting, fronts make them highly effective killers without expansion.
With a seemingly endless selection of big game rounds available to the budding hunter, making a choice may seem a bit overwhelming. What is the best round for the hunt? The answer, of course, depends on such factors as species being hunted and the likely distance at which game will be taken. As animal size and distance increases, so too should bullet velocity, diameter, and mass. Listed below are a handful of common big game cartridge options categorized by game type and hunting distance. Species type is limited to the types of North American game animals a hunter is likely to pursue (opportunities to hunt bison and grizzly bear are few and far between) and ranges are limited to a maximum of 300 yards as longer shots than that require special considerations beyond the scope of this article.
With a plethora of big game cartridges beyond the above available to hunters, there is no reason to limit one’s choices to these options. That said, ammo for the above are the most likely to be consistently available at local gun shops and big box retailers. It should also be noted that the list is a general guideline and should not be taken as gospel. A well practiced hunter might be able to ethically take deer past 150 yards with a .30-30, and a .338 Win Mag will easily kill a whitetail at 50 yards (though such a round is arguably overkill at close range). Those interested in a comprehensive real-world study of how well dozens of different rounds work on a variety of big game species would do well to peruse this site. It is important to remember that although selecting an appropriate big game round is an important part of ethical hunting, it is by no means the most important. That prize goes to the human operating the machine, as even the fastest, heaviest, most well constructed bullet can miss or cripple a game animal if the operator is careless or inept when the moment of truth arrives.