Do you adjust point of aim if target is at a different elevation

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Spade5

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I am a handgun shooter for the most part and do not hunt or shoot my AR past 100 yards and that is on more or less level ground so please humor me on this.

I was watching the movie Joe Kidd the other night. There was a bad guy up on some rocks who was shooting down on the good guys with a scoped rifle. Clint Eastwood assembles a scoped rifle that he had never shot before. So he watches for the smoke when the bad guy shoots and appears to count how long it takes to hear the round strike presumably to get the range. Then he seems to make some sort of adjustment to his scope and takes the bad guy out with one shot.

So if you are shooting at a target that is above you or below you, do you adjust your point of aim?

I seem to remember back in 1969 when I was in Infantry school getting ready to go to Nam that you either aimed above or below. Of course they also told us things like the M-16 round will rise when fired when in fact your trajectory is an arc. The enemy can use our 7.62 ammo but we cannot use theirs.
 
At distances of 100 yards or less it is not going to make much difference if you are shooting at a target above or below your position on the horizontal. Hunters and snipers shooting at distance need to adjust their point of aim or sighting device if the target is at a substantial elevation above them, or depression below them. In both cases, they need to adjust their point of aim lower.

The reason is simple. If the path of the projectile is angled from the horizontal to a considerable degree, the actual distance that the bullet travels (the actual range) will be greater than if that target was brought down or brought up to the horizontal plane. The effect of gravity on the projectile, which causes the drop, will not have as great an effect as if the bullet traveled in the horizontal plane. The portion of the bullet's path that will be fully affected by gravity will amount to the adjacent, horizontal leg of a right triangle, where the hypotenuse represents the actual range that the projectile travels. To get the portion of the bullet's path that gravity exerts its full effect on, you need to use a bit of high school trigonometry. The cosine of an angle is "a" divided by "h", where "a" is the length of the adjacent leg of a right triangle that has "h" as its hypotenuse. "H" is the actual range. "A" is the portion of the distance that gravity exerts its full effect in deflecting the bullet off its path and toward the center of the earth. In other words, the bullet will drop the same amount during its path to the target as if it had been fired on the horizontal at the shorter range "a". Since "a" is what you want to know to determine the drop, a=cos (theta) x h, where theta is the angle that the line of sight makes to the horizontal. Lets say you were shooting at someone firing at you from a window in a very tall building that was 200 yards from the muzzle of your rifle, and you had to aim upward at a 60 degree angle from the horizontal to hit that person (an extreme case so far as the angle goes). Since the cosine of 60 degrees is 0.5, you would divide your actual range in half to estimate the bullet drop. So shooting upward at a 60 degree angle will result in only half the expected bullet drop. But shooting downward at a 60 degree angle would have exactly the same result.

Of course, no bullet rises away from the bore line of a firearm. They don't have wings and can't defy gravity. They often do initially rise relative to the horizontal because the bore axis has been inclined upward from the horizontal to compensate for the drop of the bullet.
 
I believe your real "range" is r*cosine(elevation) thus the actual bullet drop will be less (bullet hits higher than expected). Uphill vs. downhill makes no difference (perhaps counter-intuitive) since effectively gravity is weakened by the angle -- same principle as pushing a load up an inclined plane as opposed to just lifting it.
 
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Anytime you're shooting uphill or downhill the horizontal distance the bullet travels is less than the actual distance. With rifles you have to be shooting pretty long distance and at a steep angle for it to make a significant difference. But anytime you're shooting up, or down the actual distance to the target is closer than you think and it is easy to shoot over. Most range finders have a built in system for figuring out the angle of the shot and will compensate for it. This is usually more of a problem for archery shooters.

In the top illustration on level ground the target is 30 yards away. In the bottom illustration a range finder would show the target as 30 yards away. But the arrow will only travel 21 horizontal yards. An archer would use his 20 yard pin when elevated and the 30 yard pin for the top illustration.

The principle is the same with rifles, but this is the best illustration I could find. Add a zero to all of the ranges and it is more realistic for rifles.

download.png
 
Good answers. To understand further, imagine shooting straight up (or down). Let's say you're on the edge of a roof-top and shooting a target 900 feet below on the street. The range to the target is 300 yards. If your rifle was zeroed at 300 yards and you put the reticle on the target, where would it impact? To hit the target, the rifle's sight would only need to be adjusted for parallax and not for any bullet drop.
 
Anytime you're shooting uphill or downhill the horizontal distance the bullet travels is less than the actual distance. With rifles you have to be shooting pretty long distance and at a steep angle for it to make a significant difference. But anytime you're shooting up, or down the actual distance to the target is closer than you think and it is easy to shoot over. Most range finders have a built in system for figuring out the angle of the shot and will compensate for it. This is usually more of a problem for archery shooters.

In the top illustration on level ground the target is 30 yards away. In the bottom illustration a range finder would show the target as 30 yards away. But the arrow will only travel 21 horizontal yards. An archer would use his 20 yard pin when elevated and the 30 yard pin for the top illustration.

The principle is the same with rifles, but this is the best illustration I could find. Add a zero to all of the ranges and it is more realistic for rifles.

View attachment 850859

Not so RE: Rifle Shooting.

It is All about Gravity - and its proportional effect on the bullet.

First off, line of sight to the target, and therefore range, is the same - uphill/downhill/level.

What changes is the gravity force vector w/r/t the bullet's line.

It's like Wind:
- 3 or 9 o'clock = full (100%) value.
- 1:30/4:30/7:30/10:30 = half (50%) value.
- 12 and 6 o'clock = zero (0.0%) value.

Just turn it on its side.

- Level = full value.
- 45 deg. (up or down) = half value.
- Straight up/down = no value.

So, > 30 deg., up or down, expect to hit high. (so aim low)




GR
 
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A few years ago I shot a mule deer ranged at 465 yards. The look angle was close to 30 degrees up from my shooting position so the horizontal distance was 402 yards. When I enter the relevant data into the Applied Ballistics app I get the following bullet drops:

465 yards @ 30 degrees > 27.5" drop (5.6 moa)
402 yards @ 0 degrees > 21.9" drop (5.3 moa)

Does 5.6" make a difference on a mule deer? Is bullet drop directly correlated to horizontal distance to the target? I would answer with possibly, and no.
 
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I am a Caribou Hunter, among talants, and I especially take advantage of high ground and the translated name of the place I hunt the Wolves that follow the Caribou is "on high'

Caribou, by habit go up mountains, Wolves follow.

When Wolves are steeply below me, and Im shooting downhill, I use the same sight setting for 150 yards to 600 and beyond.
 
A few years ago I shot a mule deer ranged at 465 yards. The look angle was close to 30 degrees up from my shooting position so the horizontal distance was 402 yards. When I enter the relevant data into the Applied Ballistics app I get the following bullet drops:

465 yards @ 30 degrees > 27.5" drop (5.6 moa)
402 yards @ 0 degrees > 21.9" drop (5.3 moa)

Does 5.6" make a difference on a mule deer? Is bullet drop directly correlated to horizontal distance to the target? I would answer with possibly, and no.

The cosine of 30 degrees is .866. If your actual distance muzzle to target was 465 yards, the component of that distance formed by the horizontal is equal to 465 x .866 = 402.7 yards. If the angle had been 60 degrees, the cosine would have been .50 and the difference in drop would have been much greater.

CosineDiagram_1000.gif

The angle theta is your angle of inclination up or down from the vertical. The hypotenuse is your actual range to target. Cosine theta is the length of "adjacent" (the horizontal leg) divided by the length of the hypotenuse. Adjacent = cosine theta x hypotenuse. The effect of gravity causing bullet drop as the projectile travels along the line of the hypotenuse will be the same as if the projectile had traveled the length of adjacent on a horizontal plane.

The difference in drop won't likely make a difference for most hunters unless the angle from the vertical is really steep and the distance is fairly long, shooting from the top of a high cliff down into a ravine, for example. Natural features like hills and mountains generally won't involve that steep an angle because earth and other substances have a "natural angle of repose". In other words, you just can't stack dirt really high like a cylinder before the top slides down the sides. In urban combat where there are windows in high buildings, you might have some pretty steep up or down angles, but the range usually won't be that great.

For those who need to make very precise shots, I understand that some rifle scopes have built-in inclinometers that will give you the angle of the sight line from the horizontal, and some even read out cosine x angle of inclination automatically.
 
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The effect of gravity causing bullet drop as the projectile travels along the line of the hypotenuse will be the same as if the projectile had traveled the length of adjacent on a horizontal plane.
except for the difference in the amount of time the force of gravity is applied to each one. the hypotenuse gets more force.

murf
 
What you are interested in is your bullet drop, in other words its departure from its pathway resulting from the force of gravity. It is true that gravity is acting on the projectile the entire time it is in flight until it hits the target or something else. But gravity pulls the projectile directly toward the center of the earth, perpendicular to the horizontal. If you shot straight up or straight down, gravity would also act on the projectile for the entire time it was in flight, but it would cause no departure from the projectile's line of flight. If gravity could somehow pull the projectile at a right angle to its line of flight, regardless of the angle of the bore axis to the horizontal, then the projectile would drop the same amount per distance regardless.
 
good , nobody said shoot high for the range(hypotenuse distance) unlike last time we saw this question in one form or another. cos of the angle(elevation or depression)x hypotenuse should give the real range . no scientific calc then shoot low for the hypotenuse , muzzle to target range.( how low is the question).
 
In all the years I have been hunting I have missed far more animals by shooting high than I ever did by shooting low. In fact, I can only remember one miss by shooting low. No matter the distance I will not shoot at an animal unless I have hair in the center of the scope. If the distance is long I may aim at the upper third of the body or if the animal is above or below I may aim at the lower third of the body but I will always have hair in the center of my scope. There's also an old saying in the military that "when the light is down, sight down."
 
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"Lights up, sights up", "lights down, sights down" is to compensate for mirage. True mirage, not the "mirage" that heat waves coming off the ground create which shooters use to estimate wind velocity.

Mirage is caused by refraction of light waves which occurs as light passes through boundaries between denser and less dense air. In bright, sunny conditions air heats up and becomes less dense, and light travels faster through it. The air directly above a hot barrel is also typically warmer and less dense than ambient air. This tends to cause a refraction of light waves up and away from the barrel. The net effect of this is to cause the target image to appear somewhat lower than it is in reality, so that the shooter must adjust the point of aim upward somewhat.

But I guess mirage is a subject for another thread.
 
No matter the distance I will not shoot at an animal unless I have hair in the center of the scope.
My dad used to put it like this: "If the animal is so far away that you think you have to hold higher than the top of his back, he's too ______ far away to be shooting at!":)
Dad has been gone for probably 10 years now, and he had to give up most of his hunting probably 10 years before that. But I still go by that rule, and I taught it to both my kids and grandkids.:)
 
pblanc said:
The cosine of 30 degrees is .866. If your actual distance muzzle to target was 465 yards, the component of that distance formed by the horizontal is equal to 465 x .866 = 402.7 yards. If the angle had been 60 degrees, the cosine would have been .50 and the difference in drop would have been much greater.

Is stating the bloody obvious your thing? I clearly stated the range to the target along with the horizontal distance so all you've done is repeat what I said and added a bunch of irrelevant crap.
 
I am a handgun shooter for the most part and do not hunt or shoot my AR past 100 yards and that is on more or less level ground so please humor me on this.

I was watching the movie Joe Kidd the other night. There was a bad guy up on some rocks who was shooting down on the good guys with a scoped rifle. Clint Eastwood assembles a scoped rifle that he had never shot before. So he watches for the smoke when the bad guy shoots and appears to count how long it takes to hear the round strike presumably to get the range. Then he seems to make some sort of adjustment to his scope and takes the bad guy out with one shot.

So if you are shooting at a target that is above you or below you, do you adjust your point of aim?

I seem to remember back in 1969 when I was in Infantry school getting ready to go to Nam that you either aimed above or below. Of course the y also told us things like the M-16 round will rise when fired when in fact your trajectory is an arc. The enemy can use our 7.62 ammo but we cannot use theirs.
It depends, how high or low, how far away to start with.

Is it something I just want to "hit" like a coyote, rat or commie? Or is it a game animal I don't want to have to chase or a gun in someone's hand pointed at one of my friends?
 
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