For those who hunt in steep canyon country, it is no secret that high-angle shooting is part science and part artform. It is also no secret that your bullet will always impact high. Take your average hunting rifle, chambered in 30-06 or .308. Zero the rifle at 100 yards on a flat surface. Now head for the hills and try shooting that rifle from way up top or way down low at a target. Your bullet will always impact high. How high the bullet will hit is determined through a little bit of old-fashioned math. But whether you are shooting uphill or downhill, your bullet is always going to impact high. This means you will have to hold low.
What it comes down to are two things, bullet drop and bullet path. Bullet drop is always measured vertically. Elevation and trajectory do not change the way bullet drop is measured. Bullet drop is always measured as a negative number, because the bullet is falling away from the bore line. Bullet path refers to what the shooter sees when he looks through the sights of his rifle. The bullet will arc, and then cross the line of sight at the selected zero. This means that bullet path is zero at the zero range, it will become negative the more that distance increases beyond the zeroed range.
Contrary to what Hollywood movies and blockbuster videogames portray, a bullet is a physical object. High-angle shots are no different than throwing other physical objects that you likely have experience with. Imagine throwing a football 10 yards on a flat grassy field. Your natural experience of gravity will impel you to throw the football high, to create an arc that will allow it to reach your receiver. Now think about standing on a mountain and throwing the same football down the mountain to the eager hands of your receiver. The distance is still 10 yards. The same arc that let you successfully complete your pass on flat land will cause the football to travel over your receiver.
This is why you will always impact high when taking those high-angled shots. When you zero your rifle on a flat plain, the bullet must create an arc to hit the bullseye. But while shooting at a high angle, uphill or downhill, the arc is different. Distance and steepness of slope will cause a greater difference in arc. This means that no matter what, when shooting at steep angles, up or down, you are going to have to hold lower than you usually would.
Modern-day rangefinders like the Leupold Rx-1200i TBR or the Leica Rangemaster CRF 1600-B offer features that can show a shooter the angle of the shot they wish to take. Some range finders will also flat out do the math that you need to compensate for the bullet drop. But if you are looking to go a little more on the cheap side of things, consider purchasing a Cosign Angle Indicator. These little devices are simple and can be mounted either directly onto your scope or onto the picatinny rail that your scope is mounted on.
A cosign angle indicator will allow you to see the numbers you require to hold low (or dial in, if that is what you prefer). For example, imagine you are set up on a big game animal at 800 yards. You are at the top of a canyon; the wind is in your favor and your angle cosine indicator gives you the number 77. You would take your distance of 800 yards and multiply it by .77. So, 800 x .77 =616 yards. This is a difference of 184 yards that you must account for in your holdover. So, even though it looks like 800 yards, you need to shoot at your target as if it is 616 yards out.
A quick and good rule of thumb is to engage any target that has a 30-degree slope, up or down, as if it were 90 percent of the actual distance. While this may not mean a whole lot of difference at 200 yards, the further out you are shooting from, the more it does matter.
Note that this is only a brief summary of high-angle shooting. For more information and cosign figure charts, check out these sites:
Remember, do the math and hold low, you’ll be good to go.