If you’re going to shoot long range in the mountains, you need to understand how angles play into the equation. Unless you’re really going long, angles less than five degrees or so don’t matter much in the grand scheme of things, but over that, you had better account for them!
I get a lot of questions concerning measuring angles, and applying them to a program to get a corrected drop formula. I use KAC’s BulletFlight (M) on an iPhone 6. To account for angle with this program, you can either manually input the angle in degrees, or simply place the phone on the scope while aiming at the target, and press the “GET” button. It will automatically populate the space with the angle. I also have Shooter on the phone, and it works similarly.
You will notice on some long range rifles a device called an Angle Cosine Indicator (ACI). The program I previously used was the Nightforce version of Exbal. Instead of degrees, cosine of the angle was used as an input. The cosine is simply the ratio of horizontal distance to slope distance. When it comes to bullet drop from gravitational pull, the bullet only cares about the horizontal distance.
As an example, I shot a wolf a couple of years ago. I was on top of a cirque looking down onto an old lake bed. I ranged the wolf at 771 yards, but the angle was 28 degrees. If you plug that into a math geek calculator, you get a cosine of .882. That means the horizontal distance of the shot was only 88% of the line of sight distance…678 yards. That’s big! A zero degree (flat ground) shot from the 338Edge +P, at 771 yards, calls for 15 MOA up. A 28 degree shot at the same distance calls for 12.8 MOA up, a difference of over 17 inches at that distance. I had about a 1 MOA target to shoot at, so without accounting for the steep angle, I would have shot quite a bit over his back, resulting in a very alive, very educated wolf.
That’s a pretty extreme example for around here, but there are plenty of hillsides I hunt where ignoring angles can result in a broken front leg or a miss over the spine, instead of a DRT scapula hit. Work the angles. Discuss this article here.