Bullets for Beginners
By Bob Beers
Throughout my life, conversations about deer hunting seem to revolve around rifles. So, when I became interested in deer hunting, that's where I started doing research. To say that I quickly became frustrated is an understatement. Rifle manufacturers don't usually indicate what their rifles are used for, except to shoot bullets from a specific cartridge.
As my investigation continued, it became evident that many rifles and cartridges are used to hunt the same animals. This really blew my mind! Why would such a wide variety of rifles and cartridges be used to shoot the same thing?
Eventually I realized that I was approaching the subject backwards. My research began with "rifles," progressed to "cartridges," then stalled with "animals." In other words, "I have a rifle, now what can I do with it?" The correct starting place is, "I want to kill a buck, how do I do that?"
At some point, it dawned on me that the bullet does the actual killing. The rifle is simply a means to deliver the bullet to the target. So, a basic knowledge of bullets seemed to be a prerequisite for studying rifles.
I discovered that bullets were not only different in caliber, but, weight, shape, and construction. I also discovered that, in simple terms, there are three basic types of bullet construction: frangible, non-expanding, and expanding. Each of these bullets has their specific purpose, so let's take a look at these three types of bullets.
Frangible bullets break up into very small pieces upon impact with the target or the background. The penetration of this type of bullet is limited and the inflicted damage is typically near the surface of the target. They are the safest type of bullet to use in semi-populated areas, as the risk of ricochet is minimized.
Frangible bullets are normally used to kill animals weighing less than approximately 30 pounds by creating significant damage within the first few inches of the impact point. (These small animals are typically called "varmints.") The frangible bullets that are typically used to hunt varmints are called "varmint bullets."
Because controlled expansion bullets and non-expanding bullets are more strongly constructed, they may simply pass through a small animal causing less than immediately lethal damage; the animal will painfully suffer as it heals or slowly dies. A humane hunter wishes neither, so frangible bullets are the ticket for hunting small animals.
Non-expanding (FMJ) bullets typically retain their general shape as the bullet penetrates and passes through target. The penetration of this type of bullet is usually much greater than frangible or expanding bullets because the frontal area of a non-expanding bullet does not increase as it penetrates.
Since the wound channel is typically much narrower than that of an expanding bullet, the damage caused by a non-expanding bullet is usually much less, and quick kills on deer size game are rare. For this reason non-expanding FMJ bullets are illegal for big game hunting almost everywhere in North America. In round nose form they are favored by some African hunters for use on the largest and toughest game, principally on elephant and rhino, where very deep penetration against heavy hide and bone is required.
A hunter's objective is normally to cause significant soft tissue damage, especially to the heart and lungs, so that the animal dies quickly, minimizing the chance of losing the kill. Non-expanding bullets do not provide that kind of performance and should not be chosen for hunting North American big game.
Expanding or "controlled expansion" bullets are designed to deform or "mushroom" as the bullet penetrates and passes through the target. Expanding bullets are the most complex and difficult type of bullet to design, and also the most useful and numerous type of bullet. Almost all big game hunting bullets are of the expanding type. The penetration of an expanding bullet may be measured in inches or feet, depending (among other things) on the bullet's design, the bullet's sectional density, the expansion medium the bullet hits, and how fast it is traveling when it hits the expansion medium.
Expanding bullets are normally used to humanely kill animals greater than approximately 30 pounds in weight by creating significant tissue damage as the bullet passes through the animal. Expanding bullets are generally constructed to (ideally) mushroom to approximately twice their initial diameter as the bullet passes through soft to firm tissue, such as skin, fat, muscle, small bones, and internal organs. The objective is to cause catastrophic damage to vital organs, especially the heart and lungs, so that the animal dies as quickly as possible.
Coaxing the optimal expansion from a bullet can be a tricky feat for the bullet designer and the hunter. For optimum expansion, the bullet must pass through tissue of approximately optimal density within the optimal speed range. There are minimum and maximum impact velocities and target densities for any expanding bullet design.
For example, no hunting bullet will penetrate and expand properly if fired at a block of armor plate; it will flatten and bounce off. Another extreme example would be to simply throw (by hand, like a mini football) an expanding hunting bullet at a block of 10% ordinance gelatin (the stuff normally used in ballistic labs to simulate living soft tissue). At such a low impact velocity the bullet would just stick in the gelatin, with no expansion at all and very little penetration. The point of these extreme examples is simply to illustrate that, to work properly, all bullets need to hit an animal of the intended type at an impact velocity that is within their intended range.
Most expanding hunting bullets have a lead alloy core protected by a jacket of some harder metal. Manufacturers vary jacket material (usually copper or a copper alloy called "gilding metal"), jacket thickness and jacket design, as well as the hardness of the lead alloy core, to control the expansion characteristics of soft point hunting bullets.
By the way, the term "soft point" refers to the lead exposed at the tip of the bullet, which helps to initiate bullet expansion upon impact with the target. There are hunting bullets that are not soft point types, but for now let's stick with those that are, as they are the kind most commonly seen. The popular Federal Soft Point, Federal/Speer Hot-Cor, Nosler Solid Base, Remington Core-Lokt, Sierra GameKing and Pro-Hunter, and Winchester Power Point are all common examples of soft point bullets found in factory loaded ammunition.
If an expanding bullet is traveling at relatively slow velocity at impact, and especially if it passes only through soft tissue, its expansion may be limited (or non-existent), behaving much like a non-expanding bullet and causing less than immediately lethal damage to the animal. (Although the poor creature may die days or even weeks later from its wound or infection.)
If an expanding bullet is traveling too fast at impact, and especially if the bullet hits a large, hard bone, it may expand so violently that its penetration ceases before it reaches the animal's vital organs. This creates a large and very painful surface wound, but less than immediately lethal damage. Once again, the animal is likely to endure great suffering and travel a considerable distance before it succumbs to its wound or is pulled down by a predator.
It seems that most expanding bullets are designed to optimally mushroom as they pass through the chest cavity (skin, fat, muscles, rib cage, lungs, and heart) of the animal for which they are intended at the average range of speeds expected at the typical hunting ranges of the cartridges for which the bullet is designed.
As an example, let's examine a 30 caliber, 150 grain expanding bullet intended for killing deer and similar size game when fired from high intensity hunting cartridges such as the .30-06 and .308 Winchester. The bullet manufacturers know that most deer are shot at 50 to 150 yards, but that many hunters shoot (or attempt to shoot) deer at 300 yards or even 400 yards, or more. And sometimes deer are killed at less than 25 yards. If we use 300 yards as the design point for the maximum expected range, then the mid-point of the expected range is halfway between 50 yards and 300 yards, or 175 yards.
A typical design impact velocity for a 30 caliber, 150 grain bullet at 175 yards as fired from a cartridge on the order of the popular .308 or .30-06 seems to be approximately 2400 feet per second. At impact speeds of about 2400 feet per second in the heart/lung area of a 150 pound deer, the front half of this bullet should mushroom to approximately 1.75 to 2 times the original diameter of the bullet and retain enough of its mass to penetrate almost all the way through the deer from side to side.
At impact speeds of approximately 2100 feet per second, although the bullet retains most of its mass, the front half of the bullet may only mushroom to approximately 1.5 times the diameter of the bullet or less. At this speed, due to the decreased expansion, the bullet is likely to shoot clear through the animal.
At impact speeds of approximately 1800 feet per second, the front half of the bullet just begins to mushroom, and, at approximately 1600 feet per second, the nose of the bullet just begins to open. These barely expanded bullets are even more likely to shoot "through and through," wasting much of their remaining energy on the scenery behind the target.
Above impact speeds in excess of approximately 2700 feet per second, our 150 grain soft point bullet may have a tendency to over expand, ultimately allowing the core to separate from the jacket. (As long as the bullet first penetrates into the animal's vitals, this is actually not a bad thing, as it increases the diameter of the wound channel.) If the bullet makes it into the heart/lung area, the result is usually a very quick kill--sometimes the "four feet in the air" kind.
At impact velocities too far over the maximum intended, our soft point bullet may fracture, fragment, or break up into small pieces, behaving much like a frangible bullet. The result is usually a wounded animal that escapes to die a lingering death. (Note: High-speed bullets of tougher design have been introduced that extend the upper limit to well over 3000 feet per second, the trade-off usually being a higher minimum impact velocity and less expansion at normal impact velocities.)
Let's see, so far we are assuming that to optimally mushroom a typical 30 caliber, 150 grain expanding bullet intended for use in cartridges on the order of the .308 Winchester and .30-06 should pass through the chest cavity "stuff" of an average size deer at an impact velocity between 2100 fps and 2700 fps, with approximately 2400 feet per second being ideal for optimum bullet performance.
As the bullet is subjected to conditions more severe than optimum (i.e., higher speeds, impact with larger bones, larger than average deer, etc.), the bullet may over-expand, thereby reducing its penetration and effectiveness. Conversely, if the bullet is subjected to conditions less severe than optimum (i.e., lower impact velocity, smaller than average deer, etc.), the bullet may under-expand or not expand at all, also reducing its effectiveness.
Expanding bullets are intended for a wide variety of animals that weigh approximately 30 pounds or more. Logic suggests that bullets normally used to kill 70 pound antelope are probably not the proper bullets to kill 1000 pound moose. Logic further suggests that, while maintaining the desired expansion characteristics, larger and tougher bullets must be used to kill larger and tougher animals.
The bullet manufacturers are fully aware of the bullet weights that hunters typically use to hunt specific animals and design the performance characteristics accordingly. Some manufacturers (Federal and Winchester in particular) indicate the intended class of game for which their bullets are intended, while others do not.
In addition to the variations of expanding bullets that we have already covered, there are five different general shapes of hunting bullets: flat point, round nose, semi-spitzer (semi-pointed), spitzer (pointed), and boat-tail spitzer (pointed with a tapered heel).
Flat point and round nose bullets have a blunt nose, the difference being merely whether it is flat or rounded. Typically, this allows a lot of lead to be exposed at the nose of the bullet, which makes for reliable expansion, especially at lower velocities. These designs also tend to penetrate in a reasonably straight line, and are reputed to be less apt to be deflected off course by intervening leaves, twigs and brush that they might encounter on their way to the target. As a consequence of their blunt nose, RN and FP bullets exhibit greater air drag, lose velocity more rapidly, and therefore exhibit a more curved trajectory.
Spitzer and semi-spitzer bullets have a pointed nose and a flat base. Spitzer bullets are sharply pointed, minimize air drag, and therefore shoot "flatter" (exhibit a less curved trajectory) than bullets with a blunt nose. But, spitzers have a tendency to tumble on impact if they don't expand, and don't initiate expansion as reliably as flat point or round nose bullets.
The most streamlined hunting bullets are boat-tail spitzer bullets. These have a pointed front-end and a tapered heel (like the stern of a sailboat). Boat-tail spitzers exhibit the least air drag and shoot flatter than the other shapes. Compared to spitzer bullets, the advantage of the boat tail is most pronounced after the bullet has fallen below the speed of sound. So the boat tail spitzer is a good design for very long range shooting, say in excess of 300 yards. Their terminal performance is similar to other spitzer bullets, but they have a reputation for more readily losing their cores.
I hope that this brief description of bullet types has been helpful. For more in depth information on the subject of bullets, see Chuck Hawks' articles in the "Bullets and Ballistics" section of the Rifle Information Page. Good Hunting!
Copyright 2006, 2012 by Bob Beers and/or chuckhawks.com. All rights reserved.