Advanced Marksmanship Vertical Dispersion in High Wind

[tnichols]

Could one of you really smart fella's explain in layman's terms why we see more vertical during high and gusty winds? I am fortunate to be able to shoot 150 plus days a year here in Hooterville IA. Range is 650 to 1K plus with SA calibers. Today for example, winds were at 10:30 at 18 gusts to 29. I was shooting my 260, and that load holds the waterline very well. Put it in todays condition, and I will typically see a bit more vertical. I was engaging targets at 775 yards and 1020 yards.

I realize that I move around a bit more in those winds (buffeting myself and the system), but that is typically more of a lateral shake/buffet than vertical. I want to be able to explain this in a nutshell to newer shooters before they go home and throw away their RCBS CM1500, change neck tension, etc...

Not looking for Litz/NASA (not that either of these folks are bad) type stuff, just a simple explanation.

Thanks

 

[ShtrRdy]

Actually it was Litz who did a simplified explanation that I could understand.

As I understand it, there are three potential vertical effects which can react from a crosswind.
1. Aerodynamic jump -- just as the bullet leaves the barrel it will yaw so that the nose is pointing toward the crosswind. It goes through a series of cycles and ends up higher if wind is from the right, (for a right twist barrel).
2. Magnus Effect -- similar to a curve ball, a crosswind flowing around a bullet will cause it to sink or rise.
3. Air flow rising or sinking over ground deflections can influence the bullet in a vertical direction.

 

[AIAW]

 

[tnichols]

Smart ass ?. I said no Litz. In all seriousness, thanks though. I have his videos, and my calc includes jump. Was just looking for an easy explanation to the newbs when they ask why, other than “trust me, I see it all the time”.

 

[AIAW]

Smart ass ?. I said no Litz. In all seriousness, thanks though. I have his videos, and my calc includes jump. Was just looking for an easy explanation to the newbs when they ask why, other than “trust me, I see it all the time”.

Hahaha! I had to do it!

 

[tnichols]

Hahaha! I had to do it!

Asshatery ??

 

[Erno86]

"Spin drift" - A left to right wind with a bullet from a right hand twist barrel --- will cause the bullet to go right an down about 4:30.

A right to wind with a bullet from a right hand twist barrel --- will cause the bullet to go left an up about 11:30.

Ya...it's a typo --- seems I don't know the difference between my right and left sometimes...

 

[Sheldon N]

"Spin drift" - A right to left wind with a bullet from a right hand twist barrel --- will cause the bullet to go right an down about 4:30.

A left to right wind with a bullet from a right hand twist barrel --- will cause the bullet to go left an up about 11:30.

I gotta get me some of these magic bullets that drift against the wind.

Also, aerodynamic jump works the opposite of what you posted. If the wind is coming from the right you will hit higher, if the wind is coming from the left you will hit lower. That's not spin drift though.

Most guys I know say the applied ballistics engine overestimates AJ so they will override their Kestrel by putting Wind1 at 0mph and just using Wind2. If the wind starts blowing hard like 15-20+mph then add something like 5-10 mph or so in Wind1. My AB Kestrel gives me about 0.1 of vertical deflection for every 5mph of wind which seems high to me.

 

[seansmd]

"A left to right wind with a bullet from a right hand twist barrel --- will cause the bullet to go left an up about 11:30."

Is this a typo?

 

[Erno86]

A right to left wind with a bullet from a right hand twist barrel will induce less loft for the bullet, but a left to right wind

"A left to right wind with a bullet from a right hand twist barrel --- will cause the bullet to go left an up about 11:30."

Is this a typo?

Ya...it's a typo --- sometimes I don't know the difference between between my right and left.

Thanks ya'll for catching my error...