Best formula for wind calculations?

[glock24]

My data-book initially consisted of a table of wind values ranging from around 3 mph to around 25 mph. It worked, but took up lots of room, could be slow to read at times, and offered only a sampling of all possible wind speed scenarios. After taking my first precision rifle class, my instructor suggested I consider reprinting my tables using wind values at <span style="text-decoration: underline">only 1 mph</span>. These values could then be multiplied by <span style="text-decoration: underline">any</span> wind speed to obtain an accurate correction value.

This sounds good, but now I have a bit of a dilemma. I've been offered two different equations for doing this, and I can't seem to convince myself if one is better (faster, simpler, or more accurate) than the other. I'm looking for some insight from folks who use data tables and calculators for wind speed.


<span style="text-decoration: underline"><span style="font-weight: bold">Option #1</span></span> - list wind values @ range in my data-book using bullet drift distances <span style="text-decoration: underline">in millimeters</span>. For example, in a 1mph wind;

100m - 3mm
500m - 41mm
1000m - 188mm

Then, to calculate wind correction (in mils) I would use the following;

<span style="font-style: italic">Actual wind speed</span> x <span style="font-style: italic">bullet drift @ 1mph</span> (from the table) divided by the <span style="font-style: italic">target range</span>.

<span style="color: #3366FF"><span style="font-weight: bold">5 mph wind x 41mm / 500m = 0.4 mils of correction</span></span>

As you can see, there are many key-strokes on the calculator with this method, but I kinda like the fact that I don't have to punch in any decimals.



<span style="text-decoration: underline"><span style="font-weight: bold">Option #2</span></span> - list wind values @ range in my data-book using bullet drift distances <span style="text-decoration: underline">in mils</span>. For example, in a 1 mph wind;

100m - 0.03 mils
500m - 0.08 mils
100m - 0.19 mils

Calculating the wind correction (in mils) is now much easier;

<span style="font-style: italic">Actual wind speed</span> x <span style="font-style: italic">bullet drift @ 1mph</span> (from table)
<span style="color: #3366FF">
<span style="font-weight: bold">5 mph wind x .08 mils = 0.4 mils of correction</span></span>

Although the math is simpler, the numbers start smaller, and the pesky decimal button comes into play.


Again, looking for any input and opinions you may have. And yes, a PDA would probably be the easiest, but I'm trying to embrace this method as (at least) a back-up plan against dead batteries.

Thanks in advance

 

[Rich Emmons]

Re: Best formula for wind calculations?

most i know do a version of #2.
I'd prefer to have 10mph as it just as easy to divide and multiply with or quarter it up.
I also have additional columns for harder math wind mphs, e.g. 7mph, 13 mph, 17mph for quick reference of common winds I shoot in.

 

[KNIGHT11B4]

Re: Best formula for wind calculations?

When using method number 2 dont worry about the decimal point until the formula is over.

Ex:
5mph wind X 8 = 40

Then just move your decimal point (invisible) over 2 and you get our .4. Makes its easier for some to do in their head.

Not a huge secret but helps people who dont commonly use math.

May help someone.

 

[desertrat1979]

Re: Best formula for wind calculations?

I have a question. I assume that all these calculations are with a full value wind. It makes sense to. Using option 2 (being the favorable method), how do you factor in less than full value angles? I know calculating wind is more art than science, but something to give a ballpark estimate helps more than a SWAG.