Range Report Range at angles

kentactic

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Minuteman
Dec 26, 2010
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i know when aiming down at a target you range to the horizontal distance not the angled distance in order to get the proper elevation adjustment. is it the same for an upward angle (target higher then you)?

kenny
 
Re: Range at angles

Both answers are not correct.

Depending on the angle and distance, an uphill shot will require a slightly different adjustment than a downhill shot at the same angle.

And the best way to shoot angles in the field is to multiply your dope for the actual distance to the target by the cosine of the angle.

For details, see:

Angled Fire Explained
 
Re: Range at angles

lindy, if they are not the same, then why would your field technique work? if i am shooting 30 degrees up or down, they will compute the same no?

can you define slight.........as in for shooting purposes is the op gonna notice as he takes a 500 yard shot at a goat for instance? thanks
 
Re: Range at angles

Go read the link, it's all there, including tables of actual error at various slopes using several computational methods. What Lindy is proposing for easy use in the field is called the "improved rifleman's rule" in the article. The technique does give the same correction whether shooting up or down. Within certain ranges and slope angles it is close enough. Read the article for more information.
 
Re: Range at angles

For typical angles and distances the differance will not be enough to measure, much less matter. If you shoot say, 2000 meters at a 60 degree angle, yes, you would have a differance that would possibly affect the outcome. At a long enough distance/angle combo, the effects of gravity and air density will be different between uphill/downhill.
 
Re: Range at angles

The difference of uphill Vs. downhill shot can be textually illustrated by what you probably already know about wind drift.

Shooting in a head wind from say 12:45clock primarily increases drag alone and thus works to slow the bullet, with only a small part of that wind energy trying to impart a sideways drift. Accordingly shooting in a tail wind form say 6:45clock reduces drag/ tries to push the bullet with only a small part of the wind energy trying to impart a drift.

These(Edit: associated vertical component) changes in trajectory are there, but so miniscule in real world shooting that they can be disregarded save for very long range, or quite fierce head/tail winds that you'd not be shooting in anyway. (Find shelter!)

Per inclined fire: it's similar. Gravity works perpendicular to the horizon. So when shooting upwards gravity is working to reduce velocity. Shooting downwards gravity is working to increase velocity and thus would change the required firing sol.

Again miniscule save for ELR.
 
Re: Range at angles

Since people apparently don't want to go read the article. From the article, computed errors for "rifleman's rule" - using dope for (slant distance times the cosine), "improved rifleman's rule" - using (dope times cosine) for the slant distance, and the method published in the Sierra reloading manual (probably too complicated to do or estimate in your head in the field).

The numbers are based on the Sierra .308 168gr HPBT at 2650fps.

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Re: Range at angles

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">For typical angles and distances the differance will not be enough to measure, much less matter.</div></div>

Correct. A good ballistic program will calculate the difference, but the difference is generally overwhelmed by other factors, including the shooter's inability to hold it...
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Re: Range at angles

thanks lindy, that was what i thought, hence my initial reply. your technical data never ceases to amaze though and is much appreciated.

<span style="text-decoration: underline"><span style="font-weight: bold">maladat</span></span> it's not that i was too lazy to read the article, in fact i did. the end result for shooting practicality however was forgetable. i wasn't sure if lindy was seeing something i wasn't.
 
Re: Range at angles

Thanks for the kind words.

Well, I study the theory and pick nits for a couple of reasons.

One is that I teach this stuff, so I'm expected to know my it.

The other is that it's easier for me to remember things if I know the principles behind them.

But the main reason is that a big part of the art of the rifle is knowing what matters and what doesn't, what factors must be compensated for, and what can be ignored, <span style="font-style: italic">on a particular shot.</span>

When you read that article, and concluded that you can, for practical purposes, ignore the difference between an uphill and a downhill shot of the same angle most of the time, you did what you need to do to learn that art.

Keep up the good work.
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Re: Range at angles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: armymedic.2</div><div class="ubbcode-body">
<span style="text-decoration: underline"><span style="font-weight: bold">maladat</span></span> it's not that i was too lazy to read the article, in fact i did. the end result for shooting practicality however was forgetable. i wasn't sure if lindy was seeing something i wasn't.</div></div>

Sorry, mea culpa!

I agree the "improved rifleman's rule" is good enough for most things. I think I am not terribly likely to ever shoot at more than a 30 degree angle at more than 1000 yards.
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You see a lot of people using horizontal distance to target, though ("rifleman's rule"), which will get you in trouble in much less extreme cases.