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Effect Of Wind On POI Vertically

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chasdicapua

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Jun 3, 2015
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Massachusetts, United States
Right hand twist barrel. Wind coming at a 90 degree angle from the right. Would it push the pellet higher as it would be bucking the spin of the pellet?

Wind coming at a 90 degree angle from the left. Would it push the pellet lower as it would be inducing more spin? 

These are just guesses. Anyone have more reliable info?!! Eventually I'm going to do some experiments with a fan to find this out. Just wanted to get an overall sense of it.
 
This is heavily slanted towards bullets and not diablo pellets.
https://en.wikipedia.org/wiki/Magnus_effect#In_external_ballistics

Also talked about some of this here:
http://www.airgunnation.com/reply/177084/
Right hand twist barrel. Wind coming at a 90 degree angle from the right. Would it push the pellet higher as it would be bucking the spin of the pellet?
Click to expand...
Pellet is spinning clockwise when looking at it from the back. Wind is coming from the right. Top of pellet is spinning into the wind. Bottom of pellet is spinning away from the wind. The low pressure area is below the pellet. The pellet will be pulled down and pushed towards the left.
Wind coming at a 90 degree angle from the left. Would it push the pellet lower as it would be inducing more spin?
Click to expand...

Pellet is spinning clockwise when looking at it from the back. Wind is coming from the left. Top of pellet is spinning away from the wind. Bottom of pellet is spinning towards the wind. The low pressure area is above the pellet. The pellet will be pulled up and pushed towards the right.
 
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6fdd1c32d4f3d214e1ba384d10466f83.jpg
I don't have any clue to the answer but please send us a picture of that fan! LOL
 
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"oldspook"This is heavily slanted towards bullets and not diablo pellets.
https://en.wikipedia.org/wiki/Magnus_effect#In_external_ballistics

Also talked about some of this here:
http://www.airgunnation.com/reply/177084/
Right hand twist barrel. Wind coming at a 90 degree angle from the right. Would it push the pellet higher as it would be bucking the spin of the pellet?
Click to expand...
Pellet is spinning clockwise when looking at it from the back. Wind is coming from the right. Top of pellet is spinning into the wind. Bottom of pellet is spinning away from the wind. The low pressure area is below the pellet. The pellet will be pulled down and pushed towards the left.
Wind coming at a 90 degree angle from the left. Would it push the pellet lower as it would be inducing more spin?
Click to expand...

Pellet is spinning clockwise when looking at it from the back. Wind is coming from the left. Top of pellet is spinning away from the wind. Bottom of pellet is spinning towards the wind. The low pressure area is above the pellet. The pellet will be pulled up and pushed towards the right.
Click to expand...
I will disagree per my own experience. Pellets do not act like fire arms rounds in the wind. if you have a clockwise or right hand twisted pellet with a wind coming from right to left the pellet will drop, up to as much as 1.5" at 55yd depending on wind speed. The opposite is true for a left to right wind, making the pellet rise. Also a pellet will rise with a tail wind and fall with a head wind. That little skirt in the back has a lot to do with how pellets react to wind. Of course every barrel is different and mileage will vary.
 
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"John_in_Ma"
"oldspook"This is heavily slanted towards bullets and not diablo pellets.
https://en.wikipedia.org/wiki/Magnus_effect#In_external_ballistics

Also talked about some of this here:
http://www.airgunnation.com/reply/177084/
Right hand twist barrel. Wind coming at a 90 degree angle from the right. Would it push the pellet higher as it would be bucking the spin of the pellet?
Click to expand...
Pellet is spinning clockwise when looking at it from the back. Wind is coming from the right. Top of pellet is spinning into the wind. Bottom of pellet is spinning away from the wind. The low pressure area is below the pellet. The pellet will be pulled down and pushed towards the left.
Wind coming at a 90 degree angle from the left. Would it push the pellet lower as it would be inducing more spin?
Click to expand...

Pellet is spinning clockwise when looking at it from the back. Wind is coming from the left. Top of pellet is spinning away from the wind. Bottom of pellet is spinning towards the wind. The low pressure area is above the pellet. The pellet will be pulled up and pushed towards the right.

Click to expand...
I will disagree per my own experience. Pellets do not act like fire arms rounds in the wind. if you have a clockwise or right hand twisted pellet with a wind coming from right to left the pellet will drop, up to as much as 1.5" at 55yd depending on wind speed. The opposite is true for a left to right wind, making the pellet rise. Also a pellet will rise with a tail wind and fall with a head wind. That little skirt in the back has a lot to do with how pellets react to wind. Of course every barrel is different and mileage will vary.
Click to expand...
:) ;) ;)
 
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Crittahatta....love it! That's what I need!!

Old Spook and John, thanks for the info. Of course, it's the opposite of what I thought!!

John, you are saying the same thing Old Spooke is saying in terms of up or down aren't you?

Pellet is spinning clockwise when looking at it from the back. Wind is coming from the right. Top of pellet is spinning into the wind. Bottom of pellet is spinning away from the wind. The low pressure area is below the pellet. The pellet will be pulled down and pushed towards the left. - Old Spook

if you have a clockwise or right hand twisted pellet with a wind coming from right to left the pellet will drop, up to as much as 1.5″ at 55yd depending on wind speed. - John
 
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My particular rifle, if i have a wind from left to right hard enough that i hold off past the 8 ring, i have to add elevation slightly 

for a right to left wind, if im holding past the 8 ring i drop elevation slightly.

i dont know the science, but i know my rifle, but i believe it has something to do with the barrel indexing. A great shooter/builder/tuner mentioned that to me once.
 
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This is pretty good But before you get to worked up about who or what is right.
How about a little reality check. You better start figuring in things like ambient temperature,
humidity levels and even the rotation of the earth. Because all of them are going to have
a bigger influence on the poi than the painfully slow rotational direction of a pellet.
On your trip to the moon you are talking about a distance that is the thickness of a sheet of paper.

CHASDICPUA As you begin to experiment with fans you better have a bunch of them.
If you could shoot down a line of them that was long enough maybe ? But you wont be able to
find any one fan powerful enough to make any change in poi that you can see. Take the lightest
slowest pellet you can and still neither you or any gun is precise enough to show the difference.
That's where the shoot long distance argument falls apart neither of you is good enough at any distance!
I encourage you to experiment, it would indeed seem logical to expect a 20 dollar box fan from wal mart
could and would move poi all over the place and it does but those movements are so incredibly small
they are undetectable. Physics is often far removed from any practical reality.

If we could shoot in controlled wind from left and from right the majority of us would see different vertical poi's
not because of pellet rotational direction ( we ain't that good) but due to the fact we all cant to some degree.
 
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Ok guys I have been taught and told all my life that pellets and bullets
are very different animals. Because of much slower speeds and twist rates
coupled with drag stabilization the influence from spin on a pellet is much
less than it is on a bullet? Is that not correct? If so and possible please
at least try to explain why. Ha ha yeah Buddha the paper thing came from 
dead center. I do not disagree am only pointing out the forces being considered
are tiny and as usual doing a poor job of it.
Did not mention the area where I do not agree and that is where the statement
was made that the pellet rises or is pushed up. Do you support that? Thanks for
any feedback and have a great day.
 
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"the influence from spin on a pellet is much
less than it is on a bullet?"

True, the influence is smaller but the total effect is made larger by the time of flight. Bullets are typically in the range of 2600-3200 FPS -/+ vs 450-650 FPS in springer range, for example. So the pellet can show a fraction of the influence at any given moment, but suffer the consequences for 4 to 5 times as long for any given distance.

An eye opener for me was the fact that a bullet fired in a vacuum perfectly horizontal will hit the ground at almost exactly the same time.
 
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Thanks Buddha Please allow me to elaborate on my limited understanding.
Right twist left wind bullet or pellet will have more lateral drift than if the wind is from
the right. Due to the rotation of the projectile. I have always been told that and for
the previous stated reasons it was more so on a bullet than a pellet? Do I know this
from running scientific test no am only parroting back the bs spewed at me.
I am hesitant to jump ship just yet.
Please consider this Lets just boil it down to an easier to grasp equation.
From gun to target bullet rotates 10 times regardless of flight time quicker it gets there
the faster it must spin. If we slow the bullet down we must also slow the spin rate.
You will no doubt see more drift in the slower bullet not so much from spin its the same.
But from longer exposure to the wind.
No need for a vacuum with a flat surface a bullet fired horizontal to it and a bullet dropped
at the same time both will hit the surface at the same time. ( gravity)
In a vacuum a bullet would never drop or loose velocity.
Thanks for the feed back I am pretty stupid and need all the help I can get! have a good en bro!!!
 
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If you have a muzzle velocity of 825 fps in a 14 fpe .177 springer (about right) with a 16 inch right hand twist rate (which seems to be common in Dianas), the rotational speed of the pellet is about 37,000 RPM. The wind speed due to rotation of the pellet is ((PI*.177)*37000)/12 ~= 1714 feet per minute. That is the speed of the pellets rotation in the air. When we convert that to MPH we get (1714*60)/5280~=19 MPH. So the effect of the lift/drag on the pellet due to rotation is the same as if the pellet were being hit by a side wind at 19 MPH. Mind you that does not mean that it will be pushed off course that much because the pellet is rotating but there is a horizontal component and it is large. We are just talking about Magnus effect here. Magnus effect is the LIFT and DRIFT caused by the pellet rotating in the air. That lift is caused because one side of the pellet is spinning INTO the wind and the other side of the pellet is spinning AWAY FROM the wind. Bernoullie's principle says that the faster a gas is moving relative to a surface the less pressure there is between that surface and the gas. In our case with a clockwise twist and a three o'clock wind the top is spinning INTO the wind at 19MPH and the bottom is spinning AWAY FROM the wind at 19MPH. The combined difference is 38MPH. Now I am sure if I had to I could work out the math but why bother? John (who is a very accomplished shooter in his own right) already did the experiment. He said up to an inch and a half at 55 yards. I'm betting on John.

There is no question that Magnus effect has as much or more effect upon pellets as it does on bullets because of longer flight times and because diablo pellets have MORE surface area and have lower sectional densities than a bullet in the same caliber, even one at the same weight. They will therefore be MORE affected by Magnus and other wind dependent gyroscopic effects than bullets given the same flight times.

Granted these effects are small but in my opinion they are MUCH larger than temperature or barometric pressure differences. One can get some pretty good estimates of these numbers in Chairgun by varying the wind and "Gyro" applet. I have calculated the stability co-efficient for an H&N FTT .177; I get 1.058 for the stability co-efficient and I calculate that the vertical component of the drift at 40 yards is 0.79 inches with a 10 MPH wind. That will be gravitational drop MINUS .79 inches with a 3 o'clock wind and gravitational drop PLUS .79 inches with a 9 o'clock wind. The horizontal drift component of that shot works out to about 2 inches and Chairgun has the total horizontal component at 2.4 inches for that shot. If we do the math in MOA or MILS (which I am not going to bother with here) we will see that the computed gyroscopic effects on a pellet are indeed larger than the same effects on a bullet which agrees with our theory that a pellet, having a lower sectional density AND more surface area than a bullet, will be affected more than the bullet.

Anyway I got to run... the network calls.
 
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old spook Thank you for your response I really do appreciate your taking
the time and making the effort to educate a monkey. I don't think we disagree
I am pretty old with the standard issue reptilian like brain. When considering
effects of spin that's all I consider. Please allow me to try and clarify im not
going to use numbers and graphs because frankly they are not needed
Imagine if you will a pipe who's interior is free from gravity and wind.
And a gun so precise it can hold zero with no deviation to the left or right.
When we send a projectile down it the projectile will slowly begin to creep
down and toward the direction of its spin. Due to a number of reasons a
bullet will do it more in a given distance than a pellet will. Due only to the effects
of spin.
As you have stated when wind is introduced every thing changes rather dramatically
When considering temperature its a matter of perspective heat the pipe and cool
the pipe with enough difference yes you will see poi effected. Barometric pressure ?
Don't think I mentioned that ? Think your referring to my statement about humidity
levels Again dependent on degrees of difference fill the pipe with water and yeah
poi is effected. 
Yes these analogies are ridiculous but no less true and based on excepted science.
I make no claims of being an expert on ballistics and its strange seemingly unending anomalies. 

My last post is very misleading and in fact dead wrong . I qualified it in my
mind by saying because of previous stated reasons. And ended up saying bullets are
more effected by wind than pellets. Geez even I know better than that.
One thing I do take issue with is when you say the bullet or pellet rises or is pushed up.
I know what you mean but that is probably not the best way to say it. The trajectory is
flatter or the drop is slowed would be more accurate because as I am sure you know
bullets and or pellets don't rise. Hey man thanks again for making the effort I don't mind
one bit when others question and or disagree because that's how we all learn. 

chasdicapua sorry man didn't intend to steel your thread or go on and on round and round largely about nothing.
 
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"fuznut"
One thing I do take issue with is when you say the bullet or pellet rises or is pushed up.
I know what you mean but that is probably not the best way to say it. The trajectory is
flatter or the drop is slowed would be more accurate because as I am sure you know
bullets and or pellets don't rise. Hey man thanks again for making the effort I don't mind
one bit when others question and or disagree because that's how we all learn. 

chasdicapua sorry man didn't intend to steel your thread or go on and on round and round largely about nothing.





Click to expand...
Chas is a real patient gentleman. I think this is the discussion he wanted to see anyway.

Yeah, it's just terminology for the most part. The trajectory is flatter but you can have a situation where a wind one direction will put you below zero and a wind the other direction will put you above zero. A good example is a problem I was working on today because of our conversation here.

I have been working with my Model 36. Chairgun says the "one point" zero is 31 yards without gyroscopic effects considered. When you include gyroscopic effects the vertical shift calculates to +0.6 inches with a wind (10 mph) from 9 o'clock and -0.6 inches with a wind from 3 o'clock. It also says that horizontal drift is +/- 1.35 inches depending on direction. When I saw that I thought, "bull hockey!" 

So I shot it today. By the way I'm talking in 1/10 MILS when I talk about clicks here. It took me a while to zero because I was shooting in a 5 to 15 mph wind switching between 9 o'clock and 10 o'clock. What I finally did was zero the rifle at 31 yards and then subtract the dope that CGP said would put me on at that range in a 10 mph wind. At that point I was theoretically zeroed for no wind at 31 yards. Then I got out my CGP dope sheet and dialed in the correction for 40 yards (-3D, -15L) and promptly shot five for five on my 40mm paddles no hold off for wind. I reset to zero and then dialed in the correction to 25 yards (-4D, -10L) and shot this target (10 on a dime) no hold off for wind:
c2974b0a7ed5b503bfb4e3a58e23b022.jpg

Then I dialed in -2L (.22" at 25 yards) and reset my turret caps to read zero. I figure being off by 2 clicks on the initial zero is reasonable at 31 yards in that kind of wind.
 
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