Serious long range shooters know every aspect of their weapon and their loads. It takes a lot of strategy to narrow into a single cartridge, then choosing the best rifle for the job (and for your wallet) isn’t easy. That’s important for the shooter that wants to be accurate over 500 or 1000 yards, but what kind of bullet you fire can make or break your performance.
Any shooter pushing long distances knows they have to compensate for bullet drop, wind drift, and even the Coriolis effect. No bullet design is going to negate all of those challenges, but with a little strategy, we can work with our bullet instead of against it. Choosing a high ballistic coefficient bullet is important for shooters, but there is more to it than just choosing the box with the highest number. If you want to be an accurate long range shooter, you need to understand the ballistic coefficient, how it affects you, how to manipulate it, and how to use it to your advantage.
Let’s start with the basics of BC,
What is a Ballistic Coefficient?
We are going to spend a whole article talking about your bullet’s ballistic coefficient, so we should define it right quick. In the simplest terms, the ballistic coefficient of any physical body is “a measure of its ability to overcome air resistance in flight” (Cornell University). It is calculated with a bullet’s mass, cross sectional area, and a drag coefficient that is determined by its design.
I don’t have to tell you that different bullet designs will have different drag coefficients. Round or flat nose bullets will not do well against drag. A bullet with a point to it will pierce through the air more easily; this is why you see a lot of polymer tips on bullets that want to still take advantage of hollow point expansion. In our use case, it doesn’t matter what that tip is made of, what is important is the overall shape of the bullet.
Drag doesn’t just have an effect on the front of an object though; tapering the bottom of a bullet further increases the ballistic coefficient. That is how you get what we call a boat tail. As you can see from the formula, the more you decrease the effects of drag, the higher your ballistics coefficient. Just about every long range shooter is going to be using a pointed bullet with a boat tail design; that is the baseline. Although there is a good bit more to explore about your ballistics coefficient that can increase your performance on the range.
Changing Your Ballistic Coefficient
The first thing that everyone thinks about with a bullet’s ballistic coefficient is drag. Although your bullet’s weight and its cross-sectional area are just as important. The first thing that you can change is your bullet weight. A heavier bullet will have a higher ballistic coefficient, all other factors held constant. That may be unexpected, but a heavier bullet carries more momentum (mass x velocity) at the same speed than a lighter one; which makes it easier to push through the air. In the same vein, a bullet with a smaller cross-sectional area, all other things held constant, would have a higher ballistic coefficient than a larger one. Cross-sectional area is also important for wind drift. The more area the wind has to push on, the further your bullet is going to drift.
The problem is that you often cannot change one of these things without changing another; it is a game of tradeoffs. Want a heavier bullet? Your cross-sectional will likely change, unless you change the material your bullet is made of, and that’s a trade off for your impact ballistics. Likewise, cross-sectional area and drag coefficient are not going to be totally independent either; change your bullet design for less drag and your area is going to change too. It’s a game of many trade offs, but a simple one.
Retaining Bullet Height On Long Range Shots
Our first goal with a high ballistic coefficient bullet is to reduce bullet drop. The more height you can retain on your flight path, the less drop you have to account for, making your job as a shooter easier. Fifth grade science says air resistance, or drag, is going to push against your bullet slowing it down until it reaches the ground. The drag coefficient portion of your ballistics coefficient is enemy number one here. This is especially true since you are shooting long distance and drag has such a long time to act on your bullet.
So obviously, we want a bullet with a high ballistic coefficient, and to do that, we need to design it to beat drag. That usually means a spire point with a boat tail. Although bullet weight and composition also play a role, and to visualize that a bit better, I plotted some data from Federal’s Ballistics Calculator that shows bullet drop over range for some fairly similar 308 cartridges. The results were interesting.
As you can see, I tried to choose bullets that weighed the same and had similar velocities; this way we can compare apples to apples. The main differences here are drag coefficients and cross sectional areas due to bullet design.
Most of these bullets had very similar ballistics, but it is worth noting that the hunters’ beloved soft point with a lower BC had noticeably more drop than the others. That’s no big surprise, no competitive long range shooter is using a soft point, but it goes to show that with equal weight and velocity, that design difference makes a big impact on your results.
The next load I wanted to point out was the Centerstrike Open Tip Match, the red line. Right off the bat, this bullet weighs more and is going slower than the others, but it doesn’t drop as much as you may expect, and even starts to out perform some other bullets across the 900 yard line. The difference is that this bullet has a high ballistics coefficient, 20% higher than the nearest competitor.
Reducing Time in Flight
The main reason you would want to use a bullet with a high ballistic coefficient as a long range shooter is to reduce your bullet’s time in flight. Let’s visualize a scenario real quick; you have one bullet with a sub par ballistic coefficient, and another one with the best ballistic coefficient on the market. Shooting them at the same distance, you see the better ballistic coefficient bullet perform better (obviously), but if you shoot the worse bullet at half the distance, it will probably move away from boresight less than the high ballistic coefficient bullet. The difference is the time in flight.
We want to compare apples to apples, so you have to shoot them at the same range, but if one bullet is faster than another and it retains that velocity longer due to a higher ballistic coefficient, it will have less time for drag and gravity to act on it. No matter what you do, drag and gravity are going to win in the end, but all other things held constant (if that were possible) a faster bullet will stay closer to boresight.
Although there is more than forward drag and gravity to worry about, your cross wind will push you left or right from boresight. This is still technically drag, but the longer your bullet is in the air, the more time the wind has to push it on its side. This is a big reason that your bullet’s cross-sectional area makes it into the ballistic coefficient calculation; it really matters!
Like I did for bullet drop, I made a graph for wind drift out to 1000 yards. We get a lot of the same results; it’s easy to see that the fatter and slower soft point experienced more drift than the other designs. The difference here is that Centerstrike Open Tipped Match is a little shorter than the others, resulting in less cross sectional area for wind to push on.
Real-World Ballistic Coefficients
As we have seen, a good ballistic coefficient is important, but it is a game of tradeoffs. Although, even after you sit down and choose your bullet carefully based on all the stats from the factory, the real world will be a bit different. Your ballistics are constantly changing depending on the weather, how your rifle is set up, which rifle you have, what kind of bullets your rifle prefers, the wind 200 400 and 800 yards down range not being identical, etc. There are a lot of caveats. Even if you are able to account for all of them, you will not be 100% perfect. That’s alright, oftentimes you can get pretty close and make a solid shot.
If you want to have the most accurate estimates possible, you should use something like Applied Ballistics or JBM Ballistics. There, you can input your muzzle velocity and velocity at the target, both measured with a chronograph. Then you can input your range and weather data, and it spits out your actual ballistic coefficient for your bullet. I would recommend using that number for any further calculations. It should be close to what the manufacturer states, but it soaks up any slack from losses due to your rifle setup.
Long Range Shooters Need a Long Range Ballistic Coefficient
Long story short, a competitive shooter wants a bullet with a high ballistic coefficient. We also saw that a lighter bullet is not always better, and that there is more to your ballistics coefficient than straight on air resistance. The science of ballistics is one of tradeoffs, but with a few minutes of strategizing, you can pick out a good bullet for your setup. The important part is that you then take real world measurements to calculate your actual ballistics coefficient and gather data for your DOPE chart. All of these things combined are going to make you as scientifically accurate as possible, the rest is left to skill.
