Promised some time ago to write something about reading conditions, as it relates to offhand shooting.   

Needed to shoot the ASSRA postal 100 Yard offhand 100 shot rim fire match. Waited too long had lots of excuses and down to the wire. On the timing, we had a large weather system move in last weekend. Strong South West with lots of rain and a bit warmer. Saturday it was at its rain peak but Sunday it cleared and blew hard 10-20 knots with higher gust.  Weather systems are like ice cubes. Large and sharp but slowly melt down to nothing.  This system was no different, Monday less wind and Tuesday I figured a shoot-able day. Perhaps later too, Wednesday turned out OK but wait too long and another system will storm through upsetting things again. Particularly in the late fall. That was the case, on Thursday the system reversed completely

Our club has several ranges. I picked range 2 which is small-bore only to 100 meters.  It lies N/E - S/W That is you are facing exactly North East which means the prevailing wind given that system should have been right on my back. Further the range is protected by high berms with trees on top behind the back stop and either side. Behind the shooting house its wide open 100 yards to a large pond and long way before anything else is going to upset the wind.

Steady wind is too good to be true though. South East forecast 5 to 10 knots is not exactly what happened. Wind runs in waves. When increasing toward 10 Knots it is more due South. Slows down more toward West.  What I found was a bit less than 10 Knots almost due south or over my right shoulder. When slowing down more West perhaps 2 or 3 knots right on my back.   Those 10 knots over my right shoulder I gave half a value. That is it affects the bullet less, half as much than if at right angles.  I keep a chart pasted to the back of my range clipboard.  Sub Sonic 22 rim fire full value wind 10 knots a little over 4 inches deviation.  7 knots Just over 3 inches 3 knots just under 1 ½ inches.  I predicted deviation with maximum gust 2 inches off on target and no deviation when the wind went right on my back and dropped off to 3 or less.

After sighing in rough. I used a fresh sighter target to shoot a group with the wind blowing at its maximum and let the group develop left of Center.   Then shot another with the wind at its minimum right on my back and very light.  That’s the one I used to fine tune my sights. Difference in the two confirmed my 2 inch off prediction.

The plan was to shoot only in the minimum condition.  It takes me a bit of time to get into position and break a shot.  Going back to my illustration of wind running in waves, it affects trees and water on the pond before it gets to the range. Picked the surface pond water as my indicator. Wind is obvious  on the waters surface and when seeing the movement knew it was time to hold my shots, see the water go flat and it’s time to get shots off. Water is good but tree leaves or grass etc can be just as good. 

From the sighter target I knew pick it wrong and I could expect a 2 inch deviation on the ASSRA target. That’s the difference in a Center 25 and a 19 or 20.  This with a very predicatable wind and less than full value wind too.  Blow harder it can cause you to miss much wider.

Shot the 100 shots Ok, any problems were not wind related.  I did watch for changes as the day progressed, this case there were none.  Often times there are changes though so do not recommend sticking to a plan no matter what.  If something had changed I would go back to the sighter target and shoot maximum adverse minimum condition to see exactly what the change would do to my bullet.  Switchbacks and changes unseen are score killers

This is also a good range for S/W wind.  N/E with higher gust it becomes a problem, the wind comes over the berm and is not real consistent as it moves down the 100 Meters.  Still the sighter proof of maximum deviation minimum deviation is the method to use.  N/E I would have moved to range 1 too. More open and less subject to unusual back currents.

With the postal match I could pick my day and location. Can’t always do that in a shoulder to shoulder match. You can steer shooting time some though and it’s essential to predict and confirm expected conditions. You need a strategy, let the expected condition set it for you.

A bit about wind flags.  I refer to them if somebody else has put some out.  They are very good indicators particularly for switchbacks gust and changes no doubt of advantage when figuring out a new shooting location.   Most of my wind strategy takes place before a record shot is fired or flags are placed though.  While shooting offhand I prefer natural signs. Trees leaves grass smoke water etc.  Google the Beaufort scale one time. It’s easy to read and very usefull.

Boats