Long Range: Downhill?

Sapper33

Sapper33

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I have the ability to set up a good sized range on my families (and their neighbors) land. I have a spot sighted where I think I could stretch it out to around 1000m. The only catch is that to have a suitable backstop, I would be firing down hill.

The spot I have picked out is about 300' above the North Sask river, and the back stop would be across the river, between 1 and 200 feet lower (I haven't ranged it yet).

How is a drop like this (call it 200' over 500m) going to affect how I would have to zero? More importantly, what kind of change would I have to make going to a flat range?
 
If you get Cosine indicator you will be able to calculate exactly what kind of slope you are shooting and run it through a ballistics program or cheat sheet and get your settings from that.
 
Your range will be shorter than your finder reads. Check out JBM ballistics. It will ask you for your angle. Then it will do the trig. for you to compensate for bullet drop.

If you dont know the angle you will be shooting, you dont have a inclometer on your rifle or in your range finder then just use a protractor on your barrel and do your best guess. Just remember one thing when using ballistic calculators. JUNK IN JUNK OUT. Meaning wich the finer accuracy of information you enter the better your solution will be.
 
(-200 divided by 1500) ACOS = 97.6623 degrees. 97.6623 SIN x 1500 = 1486.6069 feet. You will need to correct your distance by a whopping 13.39 feet at 500 yards. I wouldn't worry about it.
 
Why not? said:
Ah, the joys of high school trigonometry!

Now, is the 500 meters the hypotenuse or the base? That will make a difference, although not enough to make much difference. :D

Ted
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Since he gave a curious mixture of feet and meters I just switched the 500 meters for 500 yards, guessing that that was what he meant.

500 is the hypotenuse, the corrected number is the adjacent, and 200 is the opposite.
 
curtmg said:
SOH CAH TOA, Biotches!!!

Sine=Opposite/Hypotenuse
Cosine=Adjacent/Hypotenuse
Tangent=Opposite/Adjacent

;)
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LOL, good old trigonometry.

Simple old Pythagoras's Theorem works as well.

I was our varminting last summer shooting slightly uphill at gophers out to 350 yards. Using my altimeter on my Suunto Observer and my poor mans rangefinder (measuring wheel) I found that 58 feet of rise on a run of 350 yards worked out to a whopping 2 feet of difference.

A fun experiment but no help when it came to finding excuses for missing:redface:
 
Why not? said:
Adjacent is the correct term, not base. Hey, it's been more than fifty years! :D

Ted
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28 years for me. I do enough simple trig in the average workday that I've begun to think in those terms. Once it occurred to me that toolfaces, turnrates and winddrift were all one and the same, math actually became interesting and shooting in the wind a lot less mystifying.
 
I have done a lot of long range shooting, including on some ranges that shoot downhill. The difference in elevation required from one day to the next due to air density is so big that the small difference due to angle gets lost in the static.

The 1000 yard firing point at Stickledown, Bisley is up the side of a hill. The guy on target 65 is on top of a hill. The guy on target 1 is at the bottom of the hill. No one worries about the difference in elevation on the sights. The big problem is more wind at the top of the hill.
 
BigUglyMan said:
Kid did the math for you, right?
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Na, finding the angle is the same formula I use to pick an inclination for dropping or raising the TVD of a horizontal well in a given distance. The Sine of that angle gives the horizontal component expressed as a percentage of the measured distance which Sapper33 supplied.

A school kid would have found a simpler way to get to the same place.
 
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