Long range shooting, calculating "UP" Angle

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golfnutrlv

New member
Well, title pretty much says it all. One of the range's in my area has 1000 yard gong, but a pretty severe uphill to the target.

How do you go about calculating/figuring the up angle itself, and the correction? Is there a method, or is it just intuition and kentucky windage??? I know that you need to correct higher on an uphill, but that's about it.

I know I can just walk the round into the target, but would like to know more about it.
 
FM23-10 has a simple table (google it). Otherwise, you're stuck with either playing with a ballistics calculator or walking the shot in.

The bullet strikes higher when shooting uphill or downhill, so you'll need to come down in elevation. Angle doesn't make a major difference until you get to 20degrees or more.
 
JBM has an entry for it, "Line Of Sight Angle"

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

In reality though, ballistic calculators are never perfect, and you will most likely end up walking it in.

tahunua001 said:
you could ducktape a sextant to your rifle haha
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1270693145305.jpg
 
As it was explained to me long ago(and if I'm recalling it correctly), bullet drop will be effected only by the horizontal distance to target. While it seems counter-intuitive you need to hold slightly lower on either uphill or downhill shots than the straight line distance to the target would seem to call for. The calculations are right out of that geometry class you never thought you'd use after school.

If your target is at a 45* angle and 140 yards straight line the horizontal distance is almost 100 yards on the dot. At a 30* angle a 200 yard straight line to the target has a horizontal vector of just under 175 yards. These examples are basic 45/45/90 and 30/60/90 triangle relationships.
 
Up hill, down hill, its the same.

Determine the angle, find the cosine of that angle, mulitply the distense by that cosine, and set your sights accordingly.

Example: You're shooting 1000 yards, you have an 8 degree angle (up or down it dosn't matter).

The cosine of 8* is .990268

So your actual distance to the target is 990 yards

15* 966

Post a cosine sheet to your shooting note book. You can use your compus to determine the angle.
 
Post a cosine sheet to your shooting note book. You can use your compus to determine the angle.
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Take 90 minus your angle and then add 25 and you'll have a good enough number for our purposes. For angles 15 degrees or less, the answer is 1. The relation works up to 50 degree slope.

So for a 20 degree slope, the cosine is:
90-20+25 = 95%
 
I guess I'm dense. I can't figure out how to use the COMPASS to FIGURE THE ANGLE.
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Use the compass to draw a circle.
Divide that circle into 360 equal parts.
Super-Glue the circle to the side of your barrel.
Epoxy a carpenters level to the top of your barrel.
Hang a plumb bob from your barrel.
Adjust the rifle so the level shows the barrel is in fact level.
mark the spot on your circle where the string from the plumb bob hangs.
Aim at the uphill/downhill target.
Count the number of your 360 equal parts between the "level" mark and the current location of the plumb bob.
Contact Jethro Bodine to do the required cipherin'.
Take a shot.

Alternatively, you could use a protractor and wing it.

Alternatively alternatively, you could just eyeball it.

Alternatively alternatively alternatively, you could just shoot the damn rifle and adjust as required by the point of impact.
 
Actually many of you are stating the "riflemans rule" which works for close ranges but starts falling apart at long ranges. The easiest semi accurate way would be to used the improved riflemans rule which you would take the cosine of the angle and multiply that by the drop to the perceived distance.

So for example, if at 1000 yards your regular drop would be 32moa, but there is an 8 degree angle to it. You would do

32 * cos(8) = 31.68 moa drop.

That sill get you closer to the real drop than the regular riflemans rule. To get the exact drop you would need to use a ballistics program.... And there IS a difference between uphill and downhill.
 
The easiest way to do this, since once you get out further than nominal distances the margin for error gets incrementaly larger,is to spend a couple of bucks on a rangefinder, such as the Leupolds, that have an incidence calculator with an "adjusted range " readout. The best way to go for anything other than nominal hold under.
 
Yup.... Emcon hit it right on the nose. I'd go with the 3rd suggestion and just shoot it till you figure it out. Once you know you riffle you can do almost anything with it.
 
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