Shooting down at a target

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Balrog

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The Vegas shooting got me to wondering about the geometry of a shot like that. Shooter was about 400 yards away and 100 yards or so high. If your gun is zeroed for shooting on level ground, what does the height elevation of the shooter do to the point of impact?

Hunters in mountains would have to deal with this if they are on a mountain and game is below them.
 
Suppose someone were shooting from an elevated position at a target 400 yards from the base of the building. But if the shooter is 100 yards above the ground a range finder might give the actual range at 450-500 yards. (It is possible to do the math and get an exact range, but I'm too lazy at the moment). Even though the bullet is actually traveling the 450-500 yards, the drop would be the same as taking a 400 yard shot on level ground. In other words there would be LESS drop than you might expect.

You'd see the same thing shooting uphill as well. With a rifle you have to be shooting at pretty long range, and at a pretty steep angle for it to make a huge difference. This is actually more of an issue with archery gear.
 
It's a trigonometric function, though I took trigonometry over half a life time ago and am fuzzy on it at the moment. Basically you imagine a right triangle where your line of sight is the hypotenuse, the long side. The actual range to be compensated for is the base. This is the distance gravity will affect the projectile. Because this distance is shorter than the hypotenuse, your line of sight, bullets tend to go high.
 
Not only do you need to compensate for the difference between the hypotenuse of the triangle and the base of the triangle, you also need to adjust for sight deflection. I was thinking about this considering a scoped pellet gun for squirrels....

If squirrel is 25 yards away in the top of a tree, but the base of the tree is only ten yards away from me... not only will the bullet only drop due to gravity the equivalent of shooting at ten yards but the deflection from the scope will also be problematic. The straight line of sight needs to match the curved ballistic drop at some range. If it matches that drop at 25 yards when shooting level it will be WAY high at 25 yards up in the tree...

Shooting up and down will both have pretty much the same issue, as the acceleration due to gravity is essentially nil.
 
Captcurt said:
Really Gunny?
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A few yeas ago, on a groundhog hunt, my son had a hown hill shot at one about 125 yards. I forgot to tell him to aim just above the shoulders. His shot flipped the hog in the air and it landed on it’s back. As we were walk toward it, it jumped up and ran faster then anything I have ever seen.
He had shot right under it. Over the next two days he took several hogs, up and down hill without a miss.
 
I'm not a long distance shooter but was under the impression that when shooting down aim lower and the opposite, when shooting up aim higher.
 
jmr40 is spot on. Even in the aspect of archery. The distance on the horizontal plain is the pin you shoot. When in a stand, range the trees at the height you are in the tree. Not at the base of the tree. I’m sure at some point, there is going to be a variance. But it’s going to be a long ways.
 
i think its range muzzle to target multiply by cosine of the angle you are shooting doesnt matter if up or down. that will be the corrected range you should be holding. in other words when shooting up or down hold low if you are only using the muzzle to target distance.
 
GunnyUSMC said:
When shooting down hill, aim a little high.
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GunnyUSMC is right. Whether shooting uphill or downhill, point of impact will be higher than point of aim. I know this sounds strange but here is a short article that explains the concept.

http://www.recoilweb.com/whats-your-angle-108872.html

But, if the target is above or below your position, the corresponding angle that you’re shooting (up or down) may well require a change to your typical “flat-ground” elevation adjustment for a target at that distance in those conditions. When shooting at an angle, the bullet won’t fall as far off of its original path. Therefore, less elevation adjustment is needed in order to hit a target at an angle than a target directly in front of you. Remember it this way — if you ignore the angle, your bullet will impact high. How high depends on the degree of the angle and the target’s distance. This is true whether the target is above or below you — don’t believe me? Let’s do that math!
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EASY!

400 yards downhill on a slope, set your sights for 100 yards, and the ballistic curve is almost eliminated.
I purposely get above Caribou , Wolves and Bears when hunting in the mountains, and shoot a pretty close shooting solution that the Vegas shooters did.
I set my sights for 100 yards and hit point of aim at 400 ,easy, if the slope has a good grade to the point of 'steep'.

Makes missing with bad range estimation, or an animal running away contentiously extending that range into an easy hit.

Those poor folks were in a perfect trap.
 
RMH said:
GunnyUSMC is right. Whether shooting uphill or downhill, point of impact will be higher than point of aim. I know this sounds strange but here is a short article that explains the concept.

http://www.recoilweb.com/whats-your-angle-108872.html
Click to expand...


as mentioned with less effect of bullet drop since true distance is less (as used in the article) when shooting at an angle and you only know the muzzle to target distance you aim/shoot low than the expected drop for the muzzle to target distance. cosine of the angle multiplied by muzzle to target distance should give tou the true distance(the base of the right triangle).
 
Sticking to the subject before it's closed due to derailment, when angling a shot it's assumed there is one - 1 - target. A better example would be hunting elk in the Rockies, where you assume a position on a ridge line and are observing open ground below. Those who have hunted bighorn sheep get the opportunity to see them above, too.

Tree stand bow hunters have compensating sights which swivel to "correct" the point of aim. Those have been for sale a long time now. Scoped hunters can use stadia lines to compensate.

"Flatlanders" tend to be new to the subject. : )
 
Take it to extremes and it's easier to comprehend.

If the gun is zeroed for shooting on level ground where gravity will be pulling it from the side, take it and shoot it straight up in the air of straight down where gravity will be pulling only on the tip or base and both will impact "above" the point of aim.

Any angle between the two will be a reduced amount of shooting high but high none the less.
 
Just to clarify the question, GunnyUSMC said "hold high," and then another couple posters said "yes, point of impact is higher than expected when shooting up or down hill (paraphrasing)." So, don't you hold lower than usual if POI is higher than normal? I am wondering if I just missed something that was clear to everyone else?

Sorry if I'm slow on this.
 
RMH said:
Whether shooting uphill or downhill, point of impact will be higher than point of aim. I know this sounds strange but here is a short article that explains the concept.
Click to expand...

roval said:
as mentioned with less effect of bullet drop since true distance is less (as used in the article) when shooting at an angle and you only know the muzzle to target distance you aim/shoot low than the expected drop for the muzzle to target distance. cosine of the angle multiplied by muzzle to target distance should give tou the true distance(the base of the right triangle).
Click to expand...

Thunderchicken said:
Just to clarify the question, GunnyUSMC said "hold high," and then another couple posters said "yes, point of impact is higher than expected when shooting up or down hill (paraphrasing)." So, don't you hold lower than usual if POI is higher than normal? I am wondering if I just missed something that was clear to everyone else?
Click to expand...

I remember doing lots of shooting from the tops of levees into dug out quarries as a young adult. I learned through watching the dirt strikes to aim a little low.
 
MTMilitiaman said:
It's a trigonometric function... Because this distance is shorter than the hypotenuse, your line of sight, bullets tend to go high.
Click to expand...

GunnyUSMC said:
When shooting down hill, aim a little high.
Click to expand...

chicharrones said:
I remember doing lots of shooting from the tops of levees into dug out quarries as a young adult. I learned through watching the dirt strikes to aim a little low.
Click to expand...

Man, now this IS getting confusing. I had spoken to a fellow enthusiast a few years ago about this and he tried to explain it to me, but I think my aversion to math kept getting in the way. o_O

But, I really do hope that this thread continues until we truly figure this out. Hopefully, in layman's terms that we all can understand!
 
C5rider said:
Man, now this IS getting confusing. I had spoken to a fellow enthusiast a few years ago about this and he tried to explain it to me, but I think my aversion to math kept getting in the way. o_O

But, I really do hope that this thread continues until we truly figure this out. Hopefully, in layman's terms that we all can understand!
Click to expand...

Here's a very brief webpage that speaks to it.

http://www.chuckhawks.com/shooting_uphill.htm
 
This is assuming you are aiming at specific targets and not just spraying bullets against a lot of targets. In which case you just start spraying and watch which targets are falling and adjust accordingly.

There's a difference between shooting downhill at an elk and wildly firing at many densely packed targets to see what happens.
 
"...100 yards or so high..." 32 stories is more like 320 feet up. One story is usually and average of 10 feet. The rest is right angle triangle geometry. Not trig.
The sum of the squares of the lengths of the other two side is the hypotenuse(distance up or down at a given distance from the wall.) So at 100 yards from the wall, the distance is ~ 9366 ft.
However, like mikechandler says, the criminal in Vegas was not taking aimed shots. When hunting you hold low shooting up or down hill, not high. http://www.chuckhawks.com/shooting_uphill.htm
 
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