Tons of discussion on this. I started using this in matches and my wind calling has improved dramatically. I don't write anything for wind on the range card. I write the range and the elevation.
To make the math one less step at longer ranges, instead of doing the add a tenth at 800 etc, I determine that I have a 7 mph gun to 600, a 6 mph gun from 600-900 and a 5 mph gun from 900-1100 yds etc. Then, if I make a bad wind call and see the miss, I can correct the wind call in mph and run it on the rest of the stage. I can see the reticle in mph. I'm not saying you can't do this using the "add a tenth at 800+ method. I'm simply saying the mental math is easier for me personally if I do it as described above.
Before I learned this method I would write down what I wanted to hold for wind, but when I would miss I would have a lot harder time correcting for the targets at different distances. Instead of missing the first shot and hitting everything else, I would miss the first shot and hit the second. Then I would transition to the next target and try to guess how far my range card was off with some quick, shitty math. I would miss and then correct and hit the second shot on the second target. This would more or less repeat itself throughout the target array.
Now, I can make a wind call and shoot the first shot. If I started shooting with an 8 mph wind call, but see that I hit the edge of plate and the wind is actually 5 mph, now I can use 5 mph to do the quick math in my head for every target on the stage. Obviously, there are situations where the terrain, target angle, or gusts/lulls will dictate shooting different wind speeds throughout a stage. I find all these things much easier to manage while utilizing the bc method and doing the math in my head on every shot/target.
For those worried about the speed/accuracy, it is very easy to look at, say .6 mils on the 600 yd target and say that is 7 mph so 4 mph is just over half of that. I visualize the reticle divided in mph instead of mils if that makes any sense. A guy can make really quick adjustments and be within .1 mils of what the Kestral would have spit out. I have actually timed out less since I started using the bc method, and I've hit a lot more targets.
I'm pretty grateful there are people out there like Frank. Without this site and the podcast it would have taken me a lot longer to get to this point, if ever. There is a lot of good information being shared. It significantly shortens the learning curve vs. just going out and shooting and analysing and trying to reinvent the wheel.