Wind corrections - basic questions.

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Rodeo

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Wind - I always assumed that it was a simple carry to the right or left depending on wind direction - but did I read correctly here a few days ago that the rotation of the pellet means it rises or falls as well?
Cant find what I was reading - and it was an old post.
 
This might help

IMG_0540.webp
 
Rodeo said:
Wind - I always assumed that it was a simple carry to the right or left depending on wind direction - but did I read correctly here a few days ago that the rotation of the pellet means it rises or falls as well?
Cant find what I was reading - and it was an old post.
Click to expand...
The Magnus effect google that
 
I guess this assumes the rotation of the pellet is clockwise as you look down the range, hence no wind direction dropping the pellet down and to the left?
 
Once again, the Benchrest forum wind chart appears. Whoever put that diagram onto the Benchrest forum is an idiot who hasn't the faintest idea what they are talking about when it comes to the wind effect on spinning projectiles. The correct diagram is below.

wind chart.webp

The Benchrest chart is for bullets, not pellets.

Also, do not bother to look up Magnus, the vertical wind effect has nothing to do with Magnus, it is simply the result of the gyroscopic reaction to the pellet having to turn to face into the total airflow which is the combination of the pellet forward speed and the wind speed. There used to be a sticky explaining down wind drift but it has been taken off for some reason. The explanation for the vertical effect of a cross wind on a spinning projectile was in a thread on the old forum. It is a complex effect to explain and difficult to understand without first reading the thread on gyroscopic stability which was also on the old forum.

Perhaps I should put the threads back on this forum as there seems to be many new members who did not see them on the old forum.
 
Ballisticboy said:
Once again, the Benchrest forum wind chart appears. Whoever put that diagram onto the Benchrest forum is an idiot who hasn't the faintest idea what they are talking about when it comes to the wind effect on spinning projectiles. The correct diagram is below.

View attachment 675093
The Benchrest chart is for bullets, not pellets.



Perhaps I should put the threads back on this forum as there seems to be many new members who did not see them on the old forum.
Click to expand...
Please do mate. It's really frustrating the amount of duff info about the wind that's out there.
 
Ballisticboy said:
Once again, the Benchrest forum wind chart appears. Whoever put that diagram onto the Benchrest forum is an idiot who hasn't the faintest idea what they are talking about when it comes to the wind effect on spinning projectiles. The correct diagram is below.

View attachment 675093
The Benchrest chart is for bullets, not pellets.

Also, do not bother to look up Magnus, the vertical wind effect has nothing to do with Magnus, it is simply the result of the gyroscopic reaction to the pellet having to turn to face into the total airflow which is the combination of the pellet forward speed and the wind speed. There used to be a sticky explaining down wind drift but it has been taken off for some reason. The explanation for the vertical effect of a cross wind on a spinning projectile was in a thread on the old forum. It is a complex effect to explain and difficult to understand without first reading the thread on gyroscopic stability which was also on the old forum.

Perhaps I should put the threads back on this forum as there seems to be many new members who did not see them on the old forum.
Click to expand...
I'm curious. What happens in the Southern hemisphere where water goes down the plughole in the opposite direction to the Northern hemisphere? Does my rifling need to be in the opposite direction? Will this diagram laterally invert? Who cares?
 
Thank you.
If someone put up the maths there’s a chance I’d understand it.
But the key thing I’m missing is direction of rotation… unless all barrels rotate same way
 
And, ultimately is there a model online (or just a large equation) that will spit out something like
25mm right and 25mm low in response to these input conditions
Distance (eg 25m)
Calibre/weight
Spin direction
Velocity
Wind direction & speed
Air temperature
Density/altitude
Do I really need to care about latitude? Direction (n/s/e/w)?
anything else?

Or is it so pellet profile dependent that all we can say is here’s the general direction, do your own testing….
 
Rodeo said:
And, ultimately is there a model online (or just a large equation) that will spit out something like
25mm right and 25mm low in response to these input conditions
Distance (eg 25m)
Calibre/weight
Spin direction
Velocity
Wind direction & speed
Air temperature
Density/altitude
Do I really need to care about latitude? Direction (n/s/e/w)?
anything else?

Or is it so pellet profile dependent that all we can say is here’s the general direction, do your own testing….
Click to expand...
Pretty much every ballistic calculator will give exact expected wind drift if you input the correct details.
The wind the easiest to predict accurately in ballistic calculators

The hardest part is taking a reading of your current wind conditions to then use said calculator. The wind and weather change by the second but the physics don't😉
 
colinb said:
I'm curious. What happens in the Southern hemisphere where water goes down the plughole in the opposite direction to the Northern hemisphere? Does my rifling need to be in the opposite direction? Will this diagram laterally invert? Who cares?
Click to expand...

Isn't that, from memory, the Coriolis Effect?
 
So just a question for those that know, do the gun manufacturers make the rifling so that pellets only spin one way eg..Clockwise or do they make them so they spin in the other direction (ACW) or both and therefore you have to account for where your pellet is going to roughly land on the target. So knowing your rifling can help with prediction of how it affects your pellet when leaving the barrel against the wind ? Obviously if the wind is blowing from right to left, the pellet will deviate to the left and so forth despite the rotation of the pellet. What a subject in science this is !
Just someone who doesn't have a clue about this subject.:rolleyes:
 
Tillygti6 said:
The wind and weather change by the second
Click to expand...

Yep.😆 The range I go to on Saturdays is a often corker for challenging winds, even if the local area has light winds correctly forecast. It's great fun but there are plenty of curses uttered at times.
Like me yesterday when I'd already dropped four in a nice group into a 25mm circle whilst watching the indicator ribbon with left eye open and right eye through the scope and needing a mildot left to drift them in.
Number five landed bang on that mildot to the left when, as I squeezed the trigger, the ribbon simply died. That got a curse or two, as did the ribbon changing direction to right to left five minutes later. 😂 All part of the fun and the challenge, though.
 
Last edited:
@Ballisticboy said “The Benchrest chart is for bullets, not pellets.”

And @Tillygti6 said “Pretty much every ballistic calculator will give exact expected wind drift if you input the correct details.
The wind the easiest to predict accurately in ballistic calculators”

And the bullet / pellet charts seem to be lateral mirror images - so doesn’t that mean that most ballistics calculators are going to give the opposite effect to what I want?

I’m really missing something about what’s so special about a pellet v a bullet (or slug?)

Perhaps the easiest thing is to point me at a ballistics calculator that’s good for airgun pellets…

Thanks both!
 
Rodeo said:
And, ultimately is there a model online (or just a large equation) that will spit out something like
25mm right and 25mm low in response to these input conditions
Distance (eg 25m)
Calibre/weight
Spin direction
Velocity
Wind direction & speed
Air temperature
Density/altitude
Do I really need to care about latitude? Direction (n/s/e/w)?
anything else?

Or is it so pellet profile dependent that all we can say is here’s the general direction, do your own testing….
Click to expand...
Most online models can give you down wind drift, as @Tillygti6 says, the prediction is easy if you know exactly what the wind is doing at the time you fire, which unfortunately you never do. Some even try to predict the vertical error in a very crude approximation. It is the vertical effect which is wrong in many charts, the down wind deflection is the same.

To accurately predict the vertical deflection, you need a lot of aerodynamic data for the pellet and a six degree of freedom model.

Barrels are usually right-hand twist, but there may be some which are not. In the pellet chart I posted above, the pellets are assumed to be aerodynamically stable. Slugs and bullets are aerodynamically unstable and that is what makes the difference.
 
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