I was sitting on a ledge high above the forest, a perfect perch for spotting deer. But instead of a whitetail, a coyote came loping along directly beneath me, 40 yards away. I placed crosshairs on the animal’s chest, wondered briefly how the steep angle would affect bullet trajectory, decided I didn’t have time to worry about it, squeaked to stop the wild dog, and punched it through the lungs. The angle was so steep that the slug came out the sternum between the critter’s legs. Yet the shot didn’t strike too high or too low.
Angled shooting bothers most hunters who have trouble remembering whether bullets and slugs strike lower than usual when aiming steeply uphill or down. Common sense suggests they hit lower on uphill angles because gravity is pulling them down. Conversely, they should strike higher on downhill shots because gravity is accelerating the projectiles.
Wrong!
They strike higher either way. That’s right. Bullets land higher than normal if you shoot at steep angles up AND down. But it’s not enough to worry about in 90 percent of shooting situations.
You’d have to be taking a poke at a mountain goat 300 yards away at a 30-degree angle or more before needing to compensate for the effect of shooting at an angle — at least with modern centerfire cartridges leaving the muzzle at 2,500 fps or more. Shotgun slugs are more susceptible to angled shooting, and arrows are more sensitive yet. In fact, the slower the projectile, the more critical angled shooting becomes.
Here’s what’s going on. When you fire any projectile, it immediately begins falling due to the constant pull of gravity, which is 32 feet per second. In other words, every second the projectile falls (is pulled) faster and faster at the acceleration of 32 feet each second. This seems like a lot until you realize a .30-06 bullet going 3,000 feet per second travels 200 yards so fast that it drops just 8.8 inches when fired on the level. That’s still enough to miss a deer, so we sight our rifles to throw bullets slightly upward, much as you’d throw a football up in order for it to fly farther before reaching its target. Sight to put the bullet on target at 100 yards and it will fall just 3.2 inches at 200 yards. Sight 2 inches high at 100 and the bullet won’t fall below your aiming point until nearly 250 yards.
Shotgun slugs and arrows can’t match this because they don’t start out as fast. In addition, they slow down faster due to air drag. Traditionally, shotgun slugs are considered viable to 100 yards, beyond which they’re falling so rapidly a misjudgment in target distance of a few yards would equal a miss. Arrows are generally good for a maximum of 50 yards if the shooter can hold steadily enough and has sight pins for such extreme range.
The slower any projectile, the more critical angled shooting becomes. Climb 10 feet up a tree and fling an arrow just 30 yards and you’ll discover that the difference in its trajectory from a horizontal launch is enough to miss a deer. Experienced archers learn to aim high or sight their bows specifically for treetop angled shooting. Should shotgun shooters do the same thing? Not unless they climb to nosebleed heights. A shotgun gun spits its big slugs fast enough that angled shooting doesn’t really become a problem until the distance exceeds 100 yards and the angle 30 degrees or more. You’re not going to climb a tree high enough to gain this angle at 50 yards, let alone 100. As the range decreases the angle increases, of course, but at those closer ranges the bullet’s flight is flat enough that you won’t miss a deer-sized target with a dead-center hold. More efficient slugs (sabots, spitzer shapes) shoot flatter than full-size lead slugs and balls.
By the way, the reason all bullets strike higher when fired at extreme angles and distances (both up and down) is because gravity pulls from the center of the earth, not perpendicular to the plane of the ground. Thus, as the angle increases, the angle of “fall” or pull increases, resulting in less deviation from the line of sight than would occur over the same distance on a horizontal plane. Gravity still exerts 32 fps per second on the bullet, but a significant percentage of that pull is closer to the line of flight. Trigonometry explains it, but the easiest way to understand it is intuitively. Think of gravity pulling the bullet off its line of flight over the horizontal distance between you and your target rather than the actual distance. Thus, at a 60-degree angle uphill or downhill across 500 yards of actual distance, the equivalent horizontal distance over which the bullet would fall is just 250 yards. Aim for a 500-yard shot and you’ll shoot high. Aim for a 250-yard shot and bingo.
But what about gravity slowing down a bullet going uphill and speeding it up going downhill? Again, the speed of the projectile is so much more than the puny 32 fps speed of gravity during the microsecond flight to the target that gravity’s deceleration and acceleration don’t amount to a hill of millimeters. It’s that extreme angle that makes the big difference, and you aren’t likely to find a 100-yard shot at a 40-degree angle in the Midwest. Even in the Rockies it’s rare to get a shot at steeper than 30-degrees.
If this confuses or concerns you, by all means take some targets to your hunting spot and test the theory. Climb to your high perch, place the target at the extreme range where you anticipate a deer might appear, and shoot. See how much difference the distance and angle make compared to a horizontal shot at the same distance. Who knows, you might have one of those rare, high bluffs overlooking a distant river bottom trail so far away that the angle does require a bit of aiming change. But the average tree stand hunter in average flat to hilly terrain has nothing to worry about.
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