The Key to Shooting Far: Improving Ballistics
April 17, 2019
Encouraged by improvements in optics, rangefinders, and rifles that were developed for the military and from practical knowledge gleaned from military training, combined with reports of successful long shots, today’s riflemen are buying equipment and trying their hands at long-range shooting. Paper target punching for shot grouping or clanging a gong way out there is a lot of fun. And if you are a hunter, naturally you’ll want to apply your skills in the field.
With the right equipment, good loads, and a lot of practice, long-range shooting can teach us plenty. It teaches what it takes to make a hit and that it’s not easy without good ambient conditions, a great rangefinder that indicates scope adjustment, a solid rest, a fine hold, and ample time.
With a whole lot of practice, one learns when taking a shot is not prudent. What constitutes a long shot is different for different shooters and can change with conditions and levels of skill. Long-range shooting on game is not about taking a long shot for the sake of a long shot. Nor is it about bragging rights. It is about improving your shooting skill, with target practice being more fun than ever. It may be about setting up for a 350-yard shot that you know you can make with confidence, whereas previously you may have squeezed the trigger with only hope in your heart.
Approached with the proper perspective, practicing at long range can make you a more ethical hunter, but you first have to know what it takes to be prepared. Not only do you need to make the shot, but also you have to deliver the velocity and energy required.
Wanting to take game at longer distance is not new. The .30-30 Winchester was a faster, flatter-shooting cartridge when it was introduced. Gibbs, Ackley, and Weatherby were among a group of wildcatters who sprang up after World War II to give shooters more case capacity. Belted magnums became popular in the 1960s when the 7mm Remington Magnum and .300 Winchester Magnum were born. The idea was more powder, faster bullets, and longer distances. It did not end in the ’60s. The even bigger Ultra Mags from Remington were spawned to satisfy the demand.
Jack O’Connor and other well-known writers of the day tried to tell us that belted magnums kick too much. Wonder of wonders, rounds like the smallish 6mm and 6.5mm Creedmoor, .243 Winchester, and even the 6mm PPC are teaching today’s shooters that the big boomers are not needed to deliver a bullet accurately to great distance. It’s no secret that better shooting is easier with rounds that are not so noisy and don’t kick so much. However, when it comes to hunting, more than simple accuracy is required. Depending on the game, a cartridge needs to deliver adequate bullet energy at the target in order to dispatch the animal cleanly.
Basics of Ballistic Coefficient
Two basics are required to deliver bullet energy way down the canyon. One is muzzle velocity. The other is ballistic coefficient (BC). Much of the focus has been on muzzle velocity, hence the big cartridge cases. But improving BC is another way to get greater performance downrange without upping blast and recoil. Aside from ambient conditions, those two numbers—muzzle velocity and BC—can be used to describe a bullet’s path downrange and a lot more.
A higher BC not only means a flatter trajectory, but also more energy, higher impact velocity, less wind deflection, and a shorter time of flight. A higher BC lets you use a smaller cartridge case to get the same performance downrange. BC is a big deal.
To provide an idea of what BC is worth, I made a chart for my favorite mule deer round, the .270 Winchester Short Magnum (WSM). With reasonable loads one can get 3,300 fps velocity with a 130-grain bullet from a 24-inch barrel. You can get 3,200 fps with a 140-grain bullet, 3,100 fps with a 145-grain bullet, and 3,000 fps with a 150-grain bullet. Studying the chart, I found that every .025 of additional BC provides an additional 50 yards for delivering 1,000 foot-pounds (ft-lbs) of energy. For example, for all three of the lighter bullet weights and velocities, a BC of .500 will deliver 1,000 ft-lbs to about 1,000 yards. A BC of .475 delivers it to about 950 yards, .450 delivers to 900 yards, .425 to 850 yards, and so forth. Higher BC numbers delivered the energy even beyond 1,000 yards. Surprisingly, the heavier 150-grain bullet at 3,000 fps was about 50 yards behind the three lighter bullets.
These numbers are rounded off to make the idea easier to grasp. I picked 1,000 ft-lbs because that figure is often cited as the normal minimum impact energy when selecting a deer round. The common number for elk is 1,500 ft-lbs.
This knowledge is not lost on bullet manufacturers. Through the years they have been improving projectiles. The Nosler Ballistic Tip started the trend of making bullets with colorful and ever-sharper plastic tips. (A smaller meplat is the terminology used in the industry.) Then Swift incorporated bonding into its sleek, plastic-tipped Scirocco so that hunters would have a bullet that would not only fly flat for long range but also would hold together under the stress of high-velocity impact up close. Nosler followed with the AccuBond, and Hornady offered the InterBond.
With all the interest in long-range shooting, manufacturers have the pedal to the metal delivering long, pointy, boattailed projectiles with extraordinary BCs. Besides the Swift Scirocco II and Nosler Ballistic Tip and AccuBond, Berger’s long line of VLD (Very Low Drag) hunting bullets is very popular.
Recently, manufacturers have placed even more emphasis on long-range shooting by announcing bullets with names specifically indicating this purpose and with BCs higher than ever. Barnes has the LRX BT, the homogeneous “Long Range X-Bullet” with a boattail and a plastic tip. Nosler has the AccuBond LR for “Long Range,” an extra-long bonded bullet designed to fly flat. Hornady has the ELD-X. ELD stands for “Extra Low Drag.” Now Sierra has announced the GameChanger TGK, the “Tipped Game King.”
If bullets can be beautiful, these certainly are. They look so good that I wanted to see how they stacked up alongside some of the older bullets using real-world loads in my .270 WSM 24-inch-barreled rifle.
A Standard Test of BC
Different sources use different methods to derive BCs. A BC can describe the shape of a static bullet, or it can be based on a bullet’s flight that also incorporates the stability of the bullet. A more stable bullet produces a higher number, so BC is influenced by the gun and load as well as the bullet itself. A rifle’s rate of twist can affect bullet stability, and hence the BC of a bullet in flight, for example. Considering all of these variables, it seemed an interesting project to see how some of the highest BC bullets would compare when a single standard was used to measure all of them in flight.
The test plan was simple. Use the Oehler Model 43PBL to derive BC over 100 yards. The system measures time of flight and makes the necessary calculations to derive BC. Measuring BC requires that the spacing of the rifle’s muzzle with all the chronograph screens and the downrange target be precise. Even so, there is no swearing that the numbers received are exactly “correct.” BC is a lot like muzzle velocity published in a load manual. Printed figures are good, but to know your bullet’s velocity in your rifle you need to chronograph it yourself. Manufacturer-indicated BCs are also great indicators, but it is always far better to learn for yourself what it takes to make a hit at various distances. With an accurate load developed for my hunting rifle, I first zeroed it at 100 yards then fired the load in 100-yard increments out to 1,000 yards while noting the scope correction necessary to zero at each distance. All the shooting was good practice.
My intention for the shooting test was simply to come up with a BC for all bullets based on the same standard. I used the G1 drag function because that has been the standard for so many years and because shooters relate to it. I have read that other drag functions, such as the G7, fit these modern ultra-streamlined bullet trajectories better. However, based on my shooting at 100-yard increments, I found that a G1 function fit my hunting bullet’s curve beautifully. The best drag function to use likely depends on the specific bullet and shooting distance.
Some of the bullets in the accompanying chart have BCs higher than those indicated by their manufacturers. Most are lower. In fact, the BCs in the chart average about .02 lower than their manufacturer-indicated figures. Again, this is not to say that mine are the correct ones, it is just to say that all bullets in the chart were measured on the same standard. As such, I can make a better comparison of the bullets.
A final comment: BC is very important for long-range shooting and hunting, but when selecting a hunting bullet, remember accuracy and terminal performance also are important.