A subject that always comes up whenever hunters congregate around a campfire is that of killing power. How many times have I heard someone say: "It's where you hit 'em, not what you hit 'em with." My response to that is: You'd better make sure the bullet you hit 'em with is up to the job, or you may be faced with a long trailing chore. Then, another guy pipes up and says that his .243 is plenty of gun for deer, which convinces me he is sadly lacking in field experience. However, it is likely that his mate agrees with him and criticizes another hunter for packing an unnecessarily powerful rifle - say a 7mm magnum. In my book, no rifle in a medium caliber from .257 to .30 has too much power for even the small-boned fallow deer under uncertain conditions.
Killing power is a good subject to start an argument, but even the most powerful rifle will not kill a game cleanly unless the shooter can place a properly constructed bullet in a vital area. Today, we have a wide choice of controlled-expansion bullets in adequate weights suited for various sized game animals, so there's no good excuse for using a soft, thinly- jacketed traditional cup-and-core design that lacks penetration on a large deer.
No one can tell you how much killing power you are going to need to affect a clean kill on the next big game animal you hunt. Some hunters rely on theories, which are calculated mathematically. The best-known term of reference is kinetic energy. It measures the energy of the bullet in foot-pounds commonly used in compounding ballistic tables put out by ammunition manufacturers.
Once the weight of the bullet and its velocity are known, there's a formula for calculating its muzzle energy - square the velocity of the bullet in foot-seconds, divide by 7000 to reduce it from grains to pounds, and divide the product by twice the acceleration of gravity - 64.32. This will give the energy in foot-pounds of each grain of bullet weight. Multiply this figure by the weight of the bullet in grains and you have the muzzle energy in foot-pounds.
The second method, known as the pounds-feet theory, multiplies the muzzle velocity of the bullet by its weight in grains and divides by 7000 to reduce to pounds.
The third theory is the momentum theory. It involves using an energy multiplier in order the find the bullet's momentum. It is generally agreed that the efficient killing of deer-size animals is largely dependent on a striking energy of at least 1000 ft/lb, and that larger species like sambar and wapiti require at least 1500 ft/lbs. These are minimum energy figures but tend to substantiate them based on experience.
Few hunters realize that energy figures only make up half of the equation. For the foot stalker who takes-'em-as-they-come, (head-on, side-on or angling) reliable penetration of deer-size animals requires that the bullet strikes with a momentum figure which is equivalent to 240,000 arbitrary units.
As calculated by multiplying the bullet's weight in grains by the striking velocity in feet-per-second. Larger game such as moose and brown bears taken less than ideal conditions require at least 360,000 relative momentum units. Most experienced big-game hunters soon realize that that while kinetic energy determines a bullet's total destructive ability in volume of tissue destroyed, momentum is one of the chief determinants of penetration. These theories are all very well, but they don't always work out in practice because they disregard the design and construction of the bullet, and what is just as important, its placement. Although there is no clearly defined relationship between accuracy and killing power, the close connection quickly becomes apparent to the big-game hunter.
To put things in their proper perspective, the bullet's momentum determines the depth of the wound, while its kinetic energy determines the volume of the wound channel. If the bullet expends enough energy and destroys enough tissue, nearly any animal can be killed with a hit almost anywhere despite the bullet being misplaced. The bullet lacking in energy may drill right through the game, with little tissue destruction and allow the animal to run a long way before falling or even recover from its wound. The high-energy low-momentum bullet, on the other hand, may destroy a lot of tissue but only to a comparatively shallow depth. Such a bullet usually kills spectacularly if placed squarely in the lungs, but often fails miserably when heavy bones or thick shoulder, neck or rump muscles are encountered on the way in.
Thus, on really big game, the need for exact bullet placement becomes increasingly important. It will vary almost directly in proportion to the size and life tenacity of the quarry, but will be inversely proportional to the striking energy and momentum of the bullet - provided that bullet is up to the task.
Alas, bullet performance is never completely dependable even at moderate velocities and tends to become increasingly erratic as velocity increases.
Missionaries of the "high velocity regardless" school of thought are fond of calling attention to the manner in which their kills "drop as if pole axed," but deliberately neglect from making mention of the occasional well- hit animal that regains its feet and escapes into cover. A light high-velocity bullet that slips in between a couple of ribs and blows up in the rib cage will kill even the largest animal - often like lightning; but a sambar stag, for example, if struck in some fleshy part of his body, will almost certainly run off and be lost. While such loads rack up a number of spectacular kills, they are seldom wholly reliable except for use on small or medium-size game.
What is even worse is the very high velocity small-diameter bullets fail to produce a satisfactory blood trail from the entrance wound, in instances where the bullet fails to make exit. This is a common failing with calibers even as large as the .30 magnums when a lightly structured bullet is used. Leaving an adequate blood trail is one of the bullet's most important functions, and in heavy cover is essential to the finding of wounded game; in open country, however, a well-hit animal can usually be kept in sight until it finally goes down.
High velocity is desirable in a big-game rifle because it not only increases the bullets striking energy at long range, but also does away with the need for precise range estimation. However, when high velocity is coupled with a heavy bullet, recoil is greatly increased, something many hunters cannot handle. A high velocity rifle using lighter bullets is more pleasant to shoot, but has the disadvantage of shedding its velocity (and momentum) much faster. So that at extreme ranges where the rifle's flatter trajectory makes it easier to hit with, killing power has dropped off badly, making it much less effective against game.
It is not surprising, therefore, that mild loads like the .260 Rem., 7mm-08, and .270 Win, shooting medium weight bullets at moderately high velocity have become so popular. Without producing shoulder-bruising recoil, lightweight rifles chambering these loads are capable of making clean single-shot kills on big game out to 400 meters - much farther than the average hunter can reliably affect a lethal hit with any gun from some hastily assumed rest.
When choosing a cartridge for a specific size game you'd do well to remember that there are horses for courses. When conditions are just right, extremely high-energy, light-bullet loads kill spectacularly, but high momentum loads are by far the more reliable killers, especially when conditions are less than ideal. It pays to select a caliber and bullet that has both ample momentum and energy for the selected quarry at the expected ranges.