Advanced Marksmanship Long Range Shooter III,... long range cross-winds

[blurry6]

Hey Folks!

I d/l a copy of Long Range Shooter III and am having fun working up solutions for the various shooting scenarios - I've been doing better than I thought I'd do,... but one thing that I am having trouble with is the math involved with long-range cross-winds that occur beyond 600-yards etc. The 'wind' tutorial makes no mention of these dastardly elements and while I do fairly well 'guesstimating' their effects, I inevitably drop a point or two.

Let's say your in upper Afghanistan and glassing the hills,.. you see a taliban fighter with an RPG and decide he's gotta go. You've ranged him at 1790-yards with a 4-mph crosswind (3 o'clock) which your dope tells you to hold 0.2-MIL for each 1-mph (or 0.8-MIL). HOWEVER, after close observation you've estimated that there's a 8-10-mph (3 o'clock) wind past 700-yards,... and then a 10-14-mph (3 o'clock) past 1100-yards.

Here's the math I used in my solution:

Elevation adjustment for 1790-yards = 13.6-MIL (UP)

Wind (NOT adjusted for changing cross wind) = 0.8-MIL out to 700 yards or roughly 2/5 to target

Accounting for 8-10-mph wind from 700-1100 yards or for 400-yards of 1790-yards or roughly 15/64 the distance to target at 1.8-MIL (split 8-10-mph x 0.2-MIL).

Accounting for 10-14-mph wind from 1100-1790 yards or for 690 yards or roughly 2/5 of distance to target for 2.4-MIL (split 10-14-mph x 0.2-MIL).

Doing rough math for it as follows:

0.8-MIL x (700/1790) = .34-MIL
1.8-MIL x (400/1790) = .45-MIL
2.4-MIL x (690/1790) = .80-MIL
TOTAL = 1.7-MIL hold,....

After running it on the simulator,.. it works,... not dead-center, but it works,... Does this look rational? Is there a better(quicker) method or accounting for late-stage crosswinds?

Ry

 

[Lukas Koukal]

A real life question: Can you do the math this complicated before any of your observed winds changes?

 

[blurry6]

A real life question: Can you do the math this complicated before any of your observed winds changes?

Hah! Exactly! Short of strapping a calculator to my arm, any tricks to accounting for it other than watching for splash and correcting?

 

[Bigwheels]

I'll let FFS do the calculation for me. Untill the battery goes dead... Otherwise, I'd make my best call, )Your math looks sound) & correct from splash. Assuming I could see it ...

 

[jbailey]

take average wind of the three-
near wind: 4
mid wind: 9
far wind: 12

4+9+12 / 3 = ~8mph. 8mph * 0.2mil per mph = 1.6mils and SEND IT!

Not sure if my 0.1mil difference would hit or miss compared to your 1.7mils, but it is damn fast. 0.1mils is ~6" at 1700yds.

 

[Bigwheels]

+1. After thinking about it for a while, I think averaging the wind speed would be a better solution, & faster as well.

 

[jakelly]

Try multiplying the increase of each stage by the amount of the total distance that each increase makes up, using either fractions or percentage. It simplifies the math (vs OP) and takes into account previous wind, it would also be accurate if you shot from an area with wind, through a windless range, and into more wind. It also weights the values proportional to their input, averaging won't. In the scenario described you could use fifths as described.

So:

4(5/5) = 4 The whole range has at least 4 mph of deflection
5(3/5) = 3 The wind increase from 4 to 9 is 5 mph, the wind is at least 9 mph for 3/5 of the range
3(2/5) = 1.2 The wind increase from 9 to 12 is 3 mph, the wind is 12 mph for 2/5 of the range

8.2 So .2 mil per mph x 8.2 = 1.64 mil

You can play around within this framework using percentages or whatever (I would break this wind call down a bit differently). If you adhere to this strictly it always gives you a good starting point.

Just remember:

use corrected (for direction) wind
the smallest corrected wind value is your base, not the closest wind value
the areas of no wind need to be accounted for in fraction/percentage of total distance

YMMV, but the coulees are tough teachers.