Shooting up and down hill

Djac315 · Nov 7, 2009

I am trying to get the truth about shooting up and down hill. I have heard that it is the same as shooting on a flat plane but I have also heard that you need to compensate for it. Any input would be great thanks.

CrossHairs · Nov 7, 2009

If you are shooting up or down, you actually only adjust for the distance between you and the object along the horizontal plane because that's the distance that gravity is having an effect on your projectile.

Think of a 3, 4, 5 triangle(hopefully you remember your math classes), with the longest side (5 units) being the distance directly to your target(point to point). The shortest side (3 units) being the height above the ground and the mid dimension (the 4 units) being the distance along the ground from you to below where the object is sitting. In this case, the actual distance for adjustment would be for 4 units.....not the total distance to the object!

So, if you had sighted in at 5 units, and the object is now at four units, your going to have to adjust down accordingly.

So in real terms.....you are 50 yards from your target, but the target is 30 yards off the ground. Your gun is sighted in for 50 yards, therefore, you will have to shoot slightly lower or risk your shot going over the top.....!

I found some cool resources on the web once, but I cna't seem to locate them. a quick glance left me with this.

<broken link removed>

Inspector · Nov 10, 2009

Keep in mind that the same effect applies whether shooting up or downhill. In both cases your bullet will hit high. This boggled my mind. I couldn't get my brain around it. I finally came to understand it differently in my own mind by just looking at it as an effect of gravity. The lightbulb came on when I quit trying to understand all the drawings on the internet. I simply ran across the following statement:

"When shooting up hill or down hill the force of gravity is not fully exerted on the bullet since the bullet is not flying perpendicular to the earths surface. Therefore the gravity force when shooting up hill or down hill is less than the force exerted on the bullet when shooting flat or perpendicular to the earth. So, the bullet will NOT drop as much since the force is less.... and you would not dial as much MOA as you normally would or hold lower that you normally would at that distance."

speelyei · Nov 10, 2009

chuck hawks answers all:

Shooting Uphill and Downhill

By Chuck Hawks

The hoary old question of where to aim when shooting up or down hill regularly rears its head. It seems that many hunters understand that shooting at a steep angle changes the point of impact, but can't remember why or in which direction.

The correct answer is to hold lower than normal when shooting steeply up or down hill at long range. (At gentle angles you can ignore the problem altogether over the maximum point blank ranges of hunting rifle cartridges.)

This seems odd to many, and they insist on making the problem more difficult than it needs to be. But the reason is simple. Trajectory, the bullet's flight path, depends on the horizontal (level) range to the plane of the target, not the line of sight range up or down hill. Your eye sees the line of sight (slant) range from your position to the target, which is longer than the horizontal range.

Remember that it is gravity working on the bullet during its flight time that causes it to drop. If you were to shoot straight down, say from a tethered balloon, the bullet would have no curved trajectory, it would travel toward the earth in a straight line, just as if you simply dropped it. Likewise, if you shoot straight up, the bullet travels up in a straight line until its momentum is expended. Again, there is no curved trajectory.

You can infer from this that the farther from the level position a rifle is held when a bullet is fired, the less the bullet's drop will be over any given line of sight distance, whether it is fired up or down. Since your sights are set to compensate for bullet drop, and there is less bullet drop when shooting at an up or down angle, you must hold lower than normal to maintain the desired point of impact. For example, if you are shooting up or down at a 40 degree angle and the line of sight range is 400 yards to the target, the horizontal range is only 335 yards. 335 yards is the distance for which you must hold.

Leupold RX-III TBR display for example above.
Illustration courtesy of Leupold & Stevens,Inc.
The Leupold RX-III rangefinder that I reviewed for Guns and Shooting Online includes among its many features a mode that automatically compensates for up and down angle shots. Leupold calls this "true ballistic range" and you can set the RX-III's main readout to display the horizontal distance to the target, which is the distance you need to worry about in terms of trajectory. In the lower left corner of the display it also tells you the angle at which your are ranging and the line of sight range from your position to the target.

For example, if I range the top of a tall fir tree some distance from my house the line of sight range is 151 yards and the angle is 19 degrees of elevation, while the horizontal range--the true ballistic range--is only 130 yards. It is a neat rangefinder and a little time spent with one drives home the reality that, in terms of bullet trajectory, it is the horizontal, not the line of sight, range that matters.

Dan-Dee Sales Inc · Nov 10, 2009

They do make rangefinders that account for the angle. Just look for one that has (ARC) on the label. (Angle Range Compensation). Bushnell has one for $259.00