Here's an example:
These are my flags that I use for BR competition, set up in my back yard, spaced 5 ft. apart. They are fitted with my own double roller bearing heads, so they respond instantly to any change in wind direction.
Wind speed was from 7 'oclock and approx. 8-10 mph.
First pic is as you'd expect to see..the flags showing a steady 7 o'clock condition:
This photo was taken immediately after the first, with no 'on your body' perceptible change in wind direction and/or speed.
Not only have flags 2,3,5 and 6 moved to indicate a pretty dramatic shift in wind direction....flag #4 is now indicating a near complete headwind situation.
Other than Jim Carmichael, JB is the only 'mainstream' gun writer that gives credence to the use of flags for load work, etc.
Food for thought.....
-Al