Here's another example of using wind flags to do load work on a light barrelled hunting gun.
The gun is what I call my 'Leftovers Project'. It's a '74 vintage 700 243W barrelled action that had taken up residence in the back of the gun safe for years. I came into a herky but useable LVSF stock and rehabbed it for the project.
Here's the initial load work with 760. It starts out pretty loose but as the powder charge goes up, you can see the characteristics change. If flags hadn't been used, it would have been easy to just shoot a few at the lower end and quickly come to the wrong
conclusion that it didn't like 760. But by using flags, you know that the wind speed/direction component isn't what's driving the 'on target' performance. The powder charge is.
So it becomes relatively easy to just keep going up and let the gun tell you if it likes the powder or not. By 44.5, things were looking up and at 45.0 things really started to settle down. A few days later, I went back out and starting at 44.5, continued up to 46.5, where it started to get loose again. Since this gets used in temps from 20 degrees to 80+ (it was low 50's that day), I backed it down to 45.0 and reverified with four 5 shot groups that averaged .415.
Something else to observe on this is one more Urban Legend that should be killed off. POI/groups do not
always move up
as the powder charge increases. Barrels shake around in response to the vibration signal of the powder (all are different) and the force inparted to the lands/grooves by the amount of contact surface of that particular bullet. Heavier barrels exhibit less of this due to the fact that the physical weight of the barrel (consider it a lever) is more resistant to movement by those forces.
At 44.5 and continuing on up, the groups did start to climb higher. That's because the muzzle of the barrel is in what's referred to as the 'dwell cycle' of it's eliptical motion caused by the forces we just talked about. At the top and bottom of the dwell cycle, there is a pronounced slowing of muzzle movement as it transitions to the next up or down cycle. The muzzle being in that 'dwell area' is what we're really seeing with a nice load that shoots steady over a range of powder weights. If you're not at the 'dwell', the muzzle is more rapidly moving either up or down.....loads get fussy and inconsistent.
Here's what it looks like...the 'dwell' is the 'node' area:
Wind flags are the single biggest tool for allowing us to not only see
what's happening but also understand
what we're seeing.