How much wind does it take?

[RonS]

Seems that there is a lot of confusion about the difference between angular deflection and lateral displacement (drift). A bullet that leaves the barrel travelling North and encounters a brief pulse of East wind will be laterally displaced but still travelling North when it gets back into still air.

I'd recommend "The Wind Book For Rifle Shooters". It articulates the principals fairly clearly. A force acting upon the object in flight does change the trajectory and according to physics the object in motion will continue in that motion unless acted upon by another force. The motion caused by the wind is the addition of lateral motion to the already existing forward motion. That lateral motion will continue unless a force (wind) from the opposite direction acts upon the object. In other words, there is no such thing as lateral displacement except in conditions where opposite forces are encountered. Misreading the near wind when shooting at 1000 yards is the best way to find this out the hard way. The general recommendation from the more experienced wind readers is to gauge the near wind and compensate based on what the conditions are down range. The hard part being gauging the wind and reading the conditions down range. That's where science becomes art absent the presence of scientific instruments to tell us what is happening. Flags can only tell us so much and they often are not positioned at sufficient intervals to provide an accurate indicator. Mirage can tell us what is going on if it is present and depending on where along the course one is reading the mirage. If reading it at the target, it may or may not reflect what is going on along the rest of the course. Usually not in my experience.

 

[graywolf]

You're right, physics is relatively simple but the system variables can be so complex it's almost art. There is a lateral frictional force even in still wind.

 

[Rich Coyle]

Actually it is basic physics. Assuming all being equal except weight, more force is required to move the heavier object the same distance. Of course all things are never equal but that was the proposition.

You are not taking shape into effect.

 

[RonS]

You are not taking shape into effect.

True but I was replying to the "all other things being equal but weight" question. As you point out, things are never equal in the real world. A 300 grain 338 bullet has a higher BC (~.8 G1) verses a 140 grain 6.5 (~.6 G1). Driven out of a 338 Lapua at say 2900-3000 fps verses a 6.5 at say 2800-2900 there is no comparison, the 338 will spend less time in the air, be less affected by drag and buck the wind much better. But then the 338 consumes twice the resources at 3 times the price and you won't develop a flinch with a 6.5. My 6.5 Creedmoor load remains supersonic out past 1200 yards. That's good enough for PRS or F Class let alone hunting.