Cartridge Components Part IV (Bullets)
Of all the components of a cartridge, selecting the proper bullet for the intended purpose of the cartridge is the most critical. The purpose for which a cartridge is going to be used has little bearing on one’s choice of powder, primer, or case, but bullets are designed and constructed for specific purposes. Hunting bullets are designed for maximum terminal performance on game. Match or target bullets are manufactured to provide the highest levels of accuracy with no regard to terminal performance.
Depending on the caliber being loaded, there may be dozens of different bullets to choose from. While one must only use bullets of the proper caliber, bullets of varying weights are usually available. Within a specific caliber, a reloader can choose from a wide variety of bullet brands, types, and weights. It is usually easiest to work backwards having first decided what the bullet will be used for, then choosing weight and brand. Or, you may simply decide that you want to use a particular brand and are willing to find a load that will work with the bullets made by a certain bullet company in your caliber.
To perform reliably on game, a hunting bullet needs to expand enough to transfer energy while retaining enough weight to ensure adequate penetration to reach the vitals after passing through muscle and bone. This necessity requires hunting bullets to be constructed with thicker jackets and either bonded or divided lead cores. Monolithic copper and alloy hunting bullets also perform very well as they combine controlled expansion with near one hundred percent weight retention.
With target bullets, the only concern is how the bullet performs in flight to the target. Once the bullet has struck the target, it has done its job and it doesn’t matter how the bullet performs in regard to expansion and penetration. In general, target bullets have much thinner jackets, one-piece soft lead cores, and no bonding between the jacket and core. If a target bullet were to be used on game, it would likely expand and fragment far too quickly to achieve adequate penetration. Or, in the case of a full metal jacket or FMJ bullet, the bullet may simply pass through the animal without expanding, transferring little energy and causing minimal damage. While heavily constructed hunting bullets can and often do provide match grade accuracy, rarely do target bullets provide desirable terminal effects on big game.
For varmint hunting, rapid bullet expansion for complete energy transfer is desired. Varmint bullets are lightly constructed and designed to fragment easily upon impact providing complete energy transfer and explosive terminal performance. A bullet that will fragment readily is desirable for varmint shooting as misses are common and a bullet that will fragment quickly when it hits the ground or rocks is far less likely to skip or ricochet. Varmints are small targets, so high levels of accuracy are also desired. Price is important as well since varmint shooting is normally a high-volume affair.
When choosing a bullet, it is important to match the bullet to its purpose. Most hunting bullets will work great for punching holes in paper, but you will be needlessly wasting money. On the other hand, if you intend to hunt for large game, you won’t want to be loading target bullets even if they do shoot tiny groups out of your hunting rifle.
Bullets of a given caliber are available in a variety of weights measured in grains. More common calibers will typically have a broader range of bullet weights available where less common calibers may only be available in one or two weights. Bullet weight has a large affect on velocity and recoil. A cartridge can only produce so much energy, and this energy can either push a light bullet fast or a heavier bullet more slowly. Heavy bullets will generally retain their energy better at long range while drifting less due to wind. Heavier bullets also penetrate better due to their greater mass and higher sectional densities. Lighter bullets typically expand more rapidly due to their higher velocities.
When choosing a hunting bullet, it is important to match the bullet weight to the game you will be pursuing. Generally, the bigger the game, the heavier the bullet you will want to use. Heavy bullets work fine on smaller game, but lighter bullets typically don’t work as well on larger game. The caliber of the rifle you will be using also has an effect on what bullet weight will work for your intended game. If you are using a caliber that is considered very powerful for the game you are hunting, then your bullet weight will be less critical than if you are using a caliber that is on the lower end of the power scale. If you plan to use a smaller caliber for medium to large game, you should use the heaviest bullets available in that caliber.
Which weight bullet you choose will also be dictated by your individual rifle’s performance. All rifles will prefer a particular bullet weight. The twist rate of your rifle’s barrel will affect what weight bullets it will shoot the best. Most commercial rifle barrels are cut to a twist rate that will work well for the most common weights available in that caliber. If you start to experiment with bullets that are either very light or very heavy for caliber, you may experience performance issues due to twist rate. If you start loading much heavier bullets and accuracy drops off dramatically, it is likely that your twist rate is too slow to adequately stabilize the heavier bullets. In general, faster twist rates are necessary for stabilizing heavier bullets. If you have a choice of twist rate, it is best to pick the twist rate that will stabilize the heaviest bullet you intend to use as lighter bullets will be stabilized by it as well. One problem to consider is that a twist rate which is too fast can cause light weight, lightly constructed varmint bullets to literally spin themselves apart in mid air. As long as you are using bullets that are properly constructed for their intended use, it is more important to use the bullet that shoots the most accurately than to pick a bullet based solely on its weight.
As component costs continue to rise, price plays a bigger and bigger role in bullet selection. For hunting, the price of a bullet will always be miniscule when considered against the entire cost of a hunt, no matter how much the bullet costs. Most of the premium hunting bullets available are priced much higher than match grade bullets simply due to differences in manufacturing processes. Typically, hunting bullets require more steps during the manufacturing process than match or target bullets, which results in a higher manufacturing cost. For target shooting or competition however, price is very important as the number of total bullets required is much higher. After initial load development is complete with your chosen hunting bullet, it is far more economical to practice with a cheaper, target type bullet. While no two bullets will perform exactly the same, it should be fairly simple to develop a load which shoots very similar to your hunting load with a less expensive bullet.
Ballistic coefficient is a numerical value which provides an indication of a bullet’s ability to overcome air resistance as it travels through the air. A bullet’s ballistic coefficient tells us how aerodynamic a bullet is. Ballistic coefficient is affected by a bullets point shape, weight, ogive, length, and base style. Lately, as interest in long range hunting and marksmanship has grown, shooters and reloaders have become more aware of and interested in the importance of ballistic coefficient.
Ballistic coefficient is important as a bullet with a higher ballistic coefficient will retain its velocity and energy over a longer distance. This results in a “flatter” shooting bullet, meaning the bullet will drop less at a given range than a bullet of the same weight and muzzle velocity with a lower ballistic coefficient. Velocity retention results in greater energy on target. A bullet with a higher ballistic coefficient will also be less susceptible to the effects of wind drift.
Within normal hunting range, 300 yards or less, ballistic coefficient really isn’t a large factor in bullet performance. The advantages of a higher ballistic coefficient simply cannot be realized until the target gets out to the 600 yard mark and beyond. Of all the qualities that make a good hunting bullet, a high ballistic coefficient is the least important.
Sectional density is a mathematical value of a bullet’s weight in relation to its diameter. The reason that sectional density is important to hunters is that it provides an indication of how well a bullet will penetrate. The higher a bullet’s sectional density, the better its ability to overcome resistance when penetrating a solid medium. If velocity, diameter, and construction are equal, the bullet with the higher sectional density will penetrate more deeply. Sectional density is part of the reason heavier bullets are recommended for heavier game. In a given caliber, the heaviest bullets will have the highest sectional densities, offering the greatest penetration potential. Using sectional density to compare bullets only works well if the bullets are of the same or similar caliber. It is inaccurate to use sectional density to compare two bullets of greatly different calibers. Bullet construction must also be the same when comparing sectional densities. A varmint bullet with a high sectional density still won’t perform on large game as well as a heavily constructed hunting bullet with a lower sectional density.