In a recent post, it has been discussed how to determine a wind hold without using a Ballistic Solver.
A couple guys both explained how to determine your hold based on what's called the short wind formula or wind table.
I wanted to dive into a more thorough explanation. The above picture shows what's called the short wind table. This only works for Mils so I won't discuss MOA for this post.
The nice thing about this chart is that you can "true" or customize it to your exact round, muzzle velocity, and atmospherics.
There are two things on the chart that will change based on what bullet you are shooting.
First, is the MPH increments of the columns and second is the distance where the asterisk is located. Let's start with the MPH brackets. In this example, each bracket is graduated in multiples of 5 MPH and works well for certain .308 rifles. In order to true your MPH increments you can use one of two ways.The first way is rudimentary and will get you close but not exact. This method is using the first number in your G1 BC as your first column wind value. An example would be a G1 BC of .607 which would equal 6mph. This doesn't take into consideration variances in muzzle velocity or atmospherics and can lead to errors.
However, it's fast and mostly accurate at elevations closer to sea level. For those of you that have joined to mile+ high club, meaning you live at higher altitudes, you're better off using the second method to begin with.The second way is to use a ballistic Solver initially to build your chart. After having built your rifle with accurate data, updated the atmospherics and turned off spin drift, and set your wind to either 3:00 or 9:00, change your target distance to 500 yards (or meters).
Adjust your wind in 1mph increments until your wind hold equals as close to .5 as you can. Whatever mph gets you to .5 becomes your column value. So if you get 4mph to equal .5 at 500y, then your columns in the wind table would be 4, 8, 12, 16 etc.
The final thing to customize is the location of the asterisk. The asterisk depicts a "jump" in the graduation of your wind values. If you notice the first column, every 100yds is graduated by .1 mils. However, at 800 it jumps to .9. This is a result of rounding as not all the yardage lines equal 1/10th mil increments exactly.
To determine where your jump occurs, leave the wind at your already determined value (for this chart, 5mph) and change the target distance in 100 yd increments until you see a jump. Note that not every rifle will have a jump within the first 1000 yards.
Once you find where it jumps, from that point on, there will be more jumps and they will become more frequent.The Short Wind Table gives you the hold based on a wind from the 9:00 or 3:00 and must be adjusted based off the wind angle unless you are using mirage to determine wind speed. It also does not factor in Spin Drift. You'll need to factor these things in separately.
Special Operations Sniper Instructor.
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