BC or Bust! Does Ballistic Coefficient Matter for Hunting?

Affiliate Disclosure: This page contains affiliate links. We earn from qualifying purchases.

It was a roundnose-bullet world until 1898. The French Balle D was developed by Capt. Georges Desaleux and adopted in the 8x50 Lebel cartridge. Not only was the new French bullet sharply pointed, it was also the first known boattail design. The improved aerodynamics of the revolutionary Balle D increased maximum ranges, and most of the world’s militaries, including ours, soon shifted to pointed projectiles, often boattailed.

The German word Spitzgeschoss means “pointed bullet,” and we still use “spitzer” to differentiate a sharply pointed bullet from a roundnose or flatpoint. That says nothing about the base, which could be flat or boattailed.

The boattail reduces drag and increases a bullet’s ballistic coefficient—the index we use to judge a bullet’s ability to overcome air resistance or drag and to fly flatter. BC is the drag factor and is expressed in thousandths, as in .380 or .481. The higher the number, the lower the drag and the flatter the trajectory. When I was young, a bullet with a .481 G1 BC was high. Today’s low-drag bullets far surpass this number; some modern bullets now have G1 BCs beyond the .600s.

You might be asking where the “G1” comes from. The original concept of ballistic coefficient stems from English mathematician and clergyman Rev. Francis Bashforth’s experiments in the late 1860s. He hit upon using a “standard projectile” one inch in diameter and weighing one pound, with a flat base and conical nose.

Understanding Terms

The “G” stems from the French Gavre Commission, which analyzed firing tests of various projectiles from 1873 to 1898. Combining Bashforth’s and the commission’s efforts, we get to the G1 ballistic coefficient model, although today the G1 BC is based on a slightly modified version of Bashforth’s standard projectile.

Bashforth’s work pre-dated spitzers and boattails, as well as the higher velocities of smokeless propellants. Later experimentation showed that Bashforth’s model had variances with different bullet shapes and at different velocities. These developments eventually led to the G7 BC, which is based on a standard projectile with a boattail base, a long, tapering ogive and a sharp nose. The G7 model is closer to today’s low-drag projectiles.

Until recently, most manufacturers used G1 BC to quantify and compare their projectiles. Today, and especially with high-BC bullets that might be fired at extreme distances, G7 BCs are often used. Some manufacturers provide both. Walt Berger was probably the first to include both G1 and G7 BCs on his packaging, along with rifling twist recommendations.

Neither G1 nor G7 is perfect, due to the drag variances at different velocities. Some ballisticians solve this dilemma by adjusting values for different velocity regions. Most notably, Sierra Bullets provides three velocity-specific G1 BCs for its projectiles.

Dialed In

Numerically, the G7 value is about half the G1. So we can say that a bullet with a G7 BC of about .275 is aerodynamic, and a bullet with a G7 BC approaching .350 is a screamer. For instance, Hornady’s 175-grain ELD-X, with the highest BC listed in the accompanying chart, has a G1 of .689 and a G7 of .347.

Whichever one you choose, with today’s compact computers and ballistic apps at our fingertips, BC is wonderfully simple to apply. Know the BC, know the actual muzzle velocity, and you can essentially know the trajectory of your bullet. This is provided both numbers—and the table or program used—are accurate.

Published BCs are more correct than ever, but not all are perfect. And as range increases, even slight variations in atmospheric conditions—altitude, barometric pressure, humidity, temperature—become ever more critical. Even if starting data are perfect, which is unlikely, there are still differences in drag as velocity changes over distance. So to create perfect data, there is no substitute for shooting at actual distance.

However, whether you need perfect data depends on what you want to do. Thousand-yard competitors and shooters pushing rifle accuracy into miles need it. No ballistic app can yield such solutions; they are obtained only by extensive shooting at actual distances, constantly adjusted to shifts in atmospherics.

Time and Place

You could say that shooting at extreme distance is parallel to zeroing a rifle with a new scope. In the latter instance, you bore-sight or use a collimator or laser. You know it won’t be perfect. Your goal is simply to get bullets on paper, then adjust. For shooting at extreme range, you use a good ballistic calculator to “get on paper,” then adjust, repeat and record the data.

For me, and for many of us reading this magazine, extreme-range precision is of only clinical interest. Sure, I love to ring steel, but I’m not a competitor, and I have no desire to explore the outer limits. I’m mainly a hunter, and my target is a volleyball on deer-size game and more like a medicine ball on larger game.

I’m not an extreme-range shooter on game. I take it personally when I miss, and I’m haunted for years by wounded animals. I accept that both can happen, but I avoid uncertain shots. Sure, with today’s nearly perfect knowledge of range, plus better equipment, I can shoot farther—confidently—than was possible when I was younger. But I always have a go/no-go distance in mind, which is flexible depending on conditions.

Wind is the primary variable. Bullets with higher BCs resist wind deflection better than bullets with lower BCs. Like air resistance, wind deflection is a constant. If you know the wind speed, wind direction and deflection of your bullet, the solution can be plugged in—if the wind remains constant. There’s the rub. In the field, absent range flags, the longer the shot, the more difficult it becomes to read the wind.

Wind Bucking

Terrain channelizes wind, and the wind’s direction at the target can be different than where you’re standing—as well as between you and the target. At Tim Fallon’s SAAM shooting course in Texas, to demonstrate this they use smoke bombs in broken terrain, and I’ve seen the wind blow in three different directions across 600 yards.

It’s fun to ring steel under such conditions, but it’s too risky on game. With uncertain wind, your chances go up if you shoot a bullet that gets there quickly and minimizes wind deflection. But the bottom line is that BC can’t read the wind.

Here’s how I put BC numbers into practice. If, say, I’m preparing for a mountain hunt, I start with the best input possible. Using the manufacturer’s BC and my measured velocity, I add in expected atmospherics for where I’ll be hunting. For my purposes, medium to long range—but not extreme—it doesn’t matter much whether I use G1 or G7. Either will get me “on paper.”

Then I verify and adjust, shooting at actual distance. I make certain my data is correct far beyond any distance I’m likely to shoot. On arrival at a distant hunting destination, I check zero and verify data.

Restraint and Skill

Sometimes the shot you don’t take is as important as the shot you make. When Hornady’s ELD-X bullet was new, I set up my Jarrett .300 Win. Mag. with a 200-grain ELD-X (G1 BC .626) for a backpack sheep hunt in Alaska. I’d fired the rifle out to 900 yards and verified it on arrival.

Early on, we watched three rams vanish over a distant skyline. We caught them in a bowl in the long Arctic twilight. They were at 600 yards, and there was no way to get closer. The wind was blowing in every direction, so I never even considered a shot. We found the same group several days later, and I took the best ram at 120 yards. I didn’t need a low-drag bullet for that shot, or the magnum for that matter, but it worked.

On the other end of the spectrum, one of the toughest shots I’ve taken was on a blue sheep in Nepal. We topped a ridge and spotted a dozen rams across a valley up the next slope, just over 500 yards away. We had a howling crosswind, but we were at 15,000 feet elevation, far from camp and I was at the end of my rope. I had to consider it.

From the moving grass, it appeared the wind was quiet in the valley below, and not as strong on the next ridge. The best ram was facing left, wind blowing from right to left. I held the Zeiss Z-Plex reticle for 500 yards, with a generous sliver of daylight between rump and vertical crosshair. I hit him low behind the shoulder with my first shot from a Blaser in .300 Blaser Mag. with a Barnes TTSX bullet (G1 BC .484). I adjusted accordingly and centered the shoulder with my second. Here the high-BC round was a big help in getting it done.

Differences in Trajectory

As much as I hate doing charts, the accompanying one is worth studying because it shows what we’re up against as distance increases. My goal is to show downrange differences in trajectory and wind deflection as BC changes even slightly.

The cartridges don’t matter. BC doesn’t care about case design. Velocity matters, and the velocities are typical with either handloads or factory loads. To keep it simple, I used a tiny selection of hunting bullets that I’ve shot often. They include flatbase spitzers like the Hornady InterLock and Nosler Partition as well as the low-drag Federal Terminal Ascent and Hornady ELD-X.

The .277 choices are listed with .270 Win. velocities. The 7mms lean toward speeds in the 7mm Rem. Mag. and 7mm PRC class, and all the .30 calibers use .300 Win. Mag. velocities.

Although the bullets and BCs vary considerably, with a 200-yard zero the 400-yard drops vary by just 3.5 inches, well within the margin of error for deer-size game and most steel plates. Most experienced rifle shooters could lie down and make good 400-yard hits simply by holding high.

Variances

At 600 yards, the variance isn’t much more, but the drops range from five to six feet—meaning a verified stadia line or dialing a turret is probably best. Beyond that, though, BC starts to tell: At 1,000 yards there’s a variance of more than six feet of drop among these aerodynamic bullets. At this point you’re faced with serious math and a need for accurate inputs.

For fun, I plugged in an arbitrary 15 mph right-angle wind. Not howling but leaves and grass moving boisterously. At 400 yards, a foot to 1.5 feet into the wind will do it. At 600 yards, there are big differences, two feet to nearly four. At 1,000 yards, from six feet with my flattest-shooting choice to more than 12 feet. We can adjust for anything if we know the number, but with wind, how can we know?

Air resistance and gravity cannot be denied. Regardless of velocity and how high the BC, at some distance bullet drop and wind deflection grow from inches that we can visualize to large numbers of feet, mils or minutes of angle. Now we have a complex mathematical problem, no different than aiming long-range artillery. However, you can pre-register artillery, as you can on steel targets, but you can’t on a big game animal. You have to be right the first time.

Also, none of this speaks to accuracy. In my experience, flatbase bullets with their lower BCs often shoot tighter groups than boattails. And some rifles produce their best groups with blunt-nose bullets despite poor aerodynamics.

Simplification

However, high BC is good because it simplifies longer shots. Just keep two things in mind. First, BC doesn’t kill game. Bullet performance does. A lot of our most aerodynamic, most accurate and flattest-flying bullets are intended for target shooting, not for hunting.

If you’re looking for a hunting bullet, don’t get caught up in BC euphoria. Be sure your bullet is designed to perform on game; the flattest-flying bullet may not be the best choice. Second, regardless of what bullet you choose, remember that even the slightest breath of wind works on all projectiles every step of the way—no matter how high the BC.

---