The wind correction you make from memory, and how accurate it is.
Every rifle has its own full-value reference wind.
With that wind the correction is 0.3 mil at 300 m, 0.5 at 500, 0.6 at 600.
With the demo .308: 6.5 km/h up to 600 m, then 5 km/h up to 1000 m.
In the field there is no time for maths. The Quick Wind Factor is a number for your rifle that turns the wind into a correction you can make from memory.
For every rifle and load there is a full-value wind, at 90°, with which the correction is 0.1 mil per 100 meters: 0.3 mil at 300 m, 0.5 at 500, 0.6 at 600. If the wind is twice as strong, the correction doubles.
With the .308 of the demo profile the factor is 6.5 km/h. Here is the rule compared with the full calculation, with the app's demo profile and full-value wind at 6.5 km/h:
| Distance | Rule (mil) | Full calculation (mil) | Difference |
|---|---|---|---|
| 100 m | 0.10 | 0.09 | −0.01 |
| 200 m | 0.20 | 0.19 | −0.01 |
| 300 m | 0.30 | 0.30 | 0.00 |
| 400 m | 0.40 | 0.41 | +0.01 |
| 500 m | 0.50 | 0.54 | +0.04 |
| 600 m | 0.60 | 0.69 | +0.09 |
| 700 m | 0.70 | 0.84 | +0.14 |
| 800 m | 0.80 | 1.02 | +0.22 |
| 900 m | 0.90 | 1.22 | +0.32 |
.308, the app's demo profile, inclination angle 0°. Tolerance ±0.1 mil.
Up to 600 meters the rule stays within a tenth of a mil of the full calculation. Beyond that the gap grows: for longer distances the app offers a second number, here 5 km/h from 700 to 1000 m.
The reference wind changes with calibre, bullet and velocity. The app calculates it for your profile, tells you up to what distance it holds and shows it in the Tools, together with the Speed Drop Factor for the drop.
