Centerfire Cartridge Fundamentals for Beginners
By Bob Beers
A few years ago, my interest in firearms was rekindled. I found that I wanted to become a deer hunter. As a youngster I hunted in the southeast. Sadly, our family moved to "the city," and since then the annual M-16 re-certification training, during the few years that I was in the military, was the extent of my shooting.
As I reintroduced myself to the shooting sports with the intention of becoming a deer hunter, I initially began to research rifles. But I soon discovered that the cartridge is actually what I should learn about first. The novice deer hunter would be well advised to choose a cartridge, or at least to reduce the number of potential cartridges to two or three, before he or she begins to choose a rifle. Because the cartridge, to some extent, will dictate the type of rifle. Not all cartridges are available in all rifles, and we have to start somewhere. This article is my attempt to pass on my newly gained knowledge to other beginners.
Many people mistakenly call a cartridge a bullet, probably from watching too much TV. (NOTHING that you see on TV or in the movies relating to firearms is factually correct.) Before I knew better, I put .38 bullets in my wife's .38 Special revolver. Now, we use .38 Special cartridges with 125 grain bullets in that revolver.
A centerfire cartridge is an assembly that consists of four parts: the case, primer, propellant (powder), and a projectile (bullet). The bullet is only the part of a cartridge that flies downrange and hits the target. To a great extent, the specific components used in the construction of a cartridge, and the basic design of the cartridge, determine how far the bullet will go.
A centerfire cartridge works something like this when fired in a rifle:
The distance that a bullet can travel is significantly affected by the pressure that pushes the bullet and the weight and shape of the bullet. A given bullet can be used in many different cases. Different cases can hold different amounts of a specific propellant. The same case can hold different amounts of different propellants. (Different propellants can be used in any specific case.) And, primers with different ignition characteristics can be used in a specific case. These are all variables that affect the gas pressure generated by firing a given cartridge, and thus the flight of the bullet.
A given bullet can be propelled with a very wide range of pressures, depending on the case, primer, type of propellant, and amount of propellant used. Also, different bullets have different shapes and create different amounts of friction as they are driven through the barrel and will emerge from the muzzle at different velocities, even when they are propelled with the same case, primer, propellant, and amount of propellant. And, of course, gun barrels themselves differ in length, design, and manufacturing tolerances. No two rifle barrels, even when they are of the same brand and model, will launch bullets at the same identical velocity, even if all other factors are the same.
Fortunately, there are quite a number of well known companies that publish the important characteristics of the cartridges that they manufacture. (Federal, Remington, and Winchester are the largest of these.) Typically included in the data are the type of bullet used, the bullet weight, and the speed and trajectory of the bullet (as measured from the company's test barrel) at specific ranges. From this data, hunters can determine the suitability of the bullet for a particular purpose (such as deer hunting) and its practical maximum effective range, whether that be limited by remaining energy (800 ft. lbs. on target is generally considered a reasonable figure for humane deer kills) or trajectory.
Choosing a Deer Hunting Cartridge
Deer hunting . . . that's where we started. Let's select a deer cartridge. First, we should probably answer three questions.
"What type of bullet should be used?"
For the most humane kill, an expanding bullet is the only possible (and legal) choice. There are a great many brands and types of expanding bullets on the market. A great deal of recorded practical experience suggests that our deer killing bullet should be of at least .24 (6mm) caliber, should have a sectional density of about .200 or better, and should be carrying at least 800 ft. lbs. of kinetic energy at impact.
Fortunately for the beginner, the factories that manufacture ammunition have a very good idea of what type of bullet works best within the velocity envelope of the various deer cartridges that they offer for sale. If you follow their recommendations for any given cartridge you are unlikely to go wrong.
"How big is the average deer?"
Authorities suggest that an average whitetail buck probably weighs about 125 pounds on the hoof. The average mule deer buck probably weighs about 200 pounds, and the average Columbian blacktail buck is probably somewhere between those two in weight. A gigantic deer of any of these species might weigh as much as 350 pounds, but such deer are extremely rare. Thin-skinned animals such as deer are considered CXP2 class game.
"How far away is it, and how far can I be sure if killing it?"
The average deer in North America is killed within 100 yards. But there are areas where shots, because of the terrain and the behavior of the indigenous deer, might average twice that distance. Where I hunt, if I can get within 100 yards of a deer without spooking it, I'll be very lucky.
The answer to the second part of the question is somewhat a matter of the shooter's ability, but mostly a matter of how much the shooter practices. My shooting accuracy is acceptable to a distance of about 200 yards. So, my expected killing range is about 100 to 200 yards. (Note: The chest cavity kill zone of a whitetail deer is approximately 10 inches in diameter. My shooting practice indicates that I can consistently hit a 10 inch target at 200 yards. So, that is my limit.)
Simply stated, the cartridge of choice should be available with an expanding bullet of adequate killing power and exhibit reasonable flight characteristics through the expected range. What is meant by "reasonable flight characteristics" through my expected range of 100 to 200 yards? We know that the bullet is going to begin dropping as soon as it leaves the barrel, due to the effect of gravity. So, let's try to find a cartridge with a trajectory that, when properly zeroed, varies no more than plus or minus 3 inches from the line of sight from 0 to 200 yards. In shooters parlance, a cartridge that has a maximum point blank range (MPBR) of at least 200 yards.
Fortunately, there are many such cartridges, ranging in caliber from .24 (or 6mm) upwards. Since Remington is one of the largest and most widely distributed cartridge manufacturers, let's see what they have to offer. First, lets eliminate from consideration cartridges for which new rifles are no longer available, and all magnum, medium bore (.33 caliber to .39 caliber), and big bore (.40+ caliber) cartridges as being generally unsuitable for beginning hunters due to excessive recoil and muzzle blast. (That's a generalization, and I realize that there are always exceptions, such as the .240 Weatherby Magnum and .35 Remington, but let's just move on.)
That still leaves plenty of deer cartridges that meet or exceed my 200 yard MPBR, .24 minimum caliber, and at least 800 ft. lbs. at 200 yards requirements. Those listed in the Remington catalog include the .243 Winchester, 6mm Remington, .257 Roberts, .25-06, 6.5x55 SE, .260 Remington, 6.8mm SPC, .270 Winchester, 7x57 Mauser, 7mm-08 Remington, .280 Remington, .30-30 Winchester, .308 Winchester, .30-06 Springfield, and 8x57 Mauser. With the proper load and bullet, any of these cartridges will cleanly harvest all North American Deer.
As a general rule, the smaller caliber cartridges kick less than the larger calibers because they shoot lighter bullets. Likewise, within any given caliber, cartridges that shoot the same weight bullet at higher velocity kick more than those that develop less velocity. This is important because recoil degrades accuracy, and accurate bullet placement is, by far, the most important factor in killing power. Also, it is simply more fun to practice with a rifle that kicks less. And, not only does practice make perfect, the whole point of shooting--like any sport--is to have fun.
So the beginning shooter is well advised to choose a deer cartridge that he or she does not find intimidating to shoot. Among the best choices for anyone concerned about recoil are the .243 Win, 6mm Rem, .25-35 Win, .257 Roberts, 6.5x55, and .260 Rem. The hunter that might also wish to hunt elk or other large animals with the same rifle and is less concerned about recoil might consider one of the powerful "all-around" calibers, such as the .270 Win, .308 Win, or .30-06.
In the event, I chose the .308 Winchester--one of the most popular, versatile, and widely available rifle cartridges in the world--as my deer cartridge. Whatever your choice in cartridges, after you buy your deer rifle, practice, practice, practice! Good Hunting!
Copyright 2006 by Bob Beers. All rights reserved.