How do you judge wind

[Eagle Six]

It's a starting place.

Hypothetically, lets say the first third of the distance is equal to the last two thirds. Now lets also assume we have a 10mph l-r wind for the first third and a 10mph r-l for the 2nd 2/3rds. Now, would you hold in the middle?

Please explain this, "lets say the first third of the distance is equal to the last two thirds".


I can illustrate this, "Now lets also assume we have a 10mph l-r wind for the first third and a 10mph r-l for the 2nd 2/3rds. Now, would you hold in the middle?"

 

[gunsandgunsmithing]

Please explain this, "lets say the first third of the distance is equal to the last two thirds".


I can illustrate this, "Now lets also assume we have a 10mph l-r wind for the first third and a 10mph r-l for the 2nd 2/3rds. Now, would you hold in the middle?"

Let's say it's 300 to the target and in the scenario in post 27, I weighted it to where the first 100 yards is SAME VALUE as the last 200 yards...iow, the drift from the muzzle to 100 should be equal to the drift from 100 to 300. This scenario should yield a dead on hold. Make sense now?

 

[gunsandgunsmithing]

The lateral trajectory of a bullet under the influence of wind will be a curve, not a straight line. If the influence of the wind stops at some point on the way to the intended target, the bullet will continue moving offline on the tangent line to that initial curve at whatever point the wind effect stopped. This is because of bullet rotation, the weathervane effect, and the resultant drag effect that are what actually cause the bullet to move offline under the influence of wind.

I think you're splitting a fine hair. Be it a bullet or a weathervane, drag makes it move. A bullet will almost instantly turn and point INTO the wind regardless of which direction it spins or the direction of the wind. I'm not sure the rotational direction is enough of a factor to consider at this point of this discussion. Not saying it has zero effect but there are far bigger factors.

 

[gunsandgunsmithing]

Please explain this, "lets say the first third of the distance is equal to the last two thirds".


I can illustrate this, "Now lets also assume we have a 10mph l-r wind for the first third and a 10mph r-l for the 2nd 2/3rds. Now, would you hold in the middle?"

Oops..I edited my reply. I just misspoke

 

[Eagle Six]

Let's say it's 300 to the target and in the scenario in post 27, I weighted it to where the first 100 yards is twice as important as the last 200 yards...iow, the drift from the muzzle to 100 should be equal to the drift from 100 to 300. This scenario should yield a dead on hold. Make sense now?

Yes I understand your edit, except it wouldn't. The bullet has no push once pressure is released at the muzzle, it only has momentum. The further it travels drag will reduce the momentum (speed) and the wind will have more effect on the direction as the bullet decreases speed. Also in effect are the influence as stated by @Ned Ludd as well as other elements. If you want to use straight lines and for simplification I will make some calculations and see what I come up with.

 

[dcali]

From what I’m reading you can have a accurate, rifle and ammo, but if you can’t read the wind your toast at a match

For precision disciplines (BR and F class), given a properly set up rifle, it's all that matters. And everyone at the top will have a properly set up rifle.

 

[Iowa Fox]

Listen to your spotter it's his call.

 

[Ned Ludd]

Here is a more visual representation of my previous statement. The trajectory due to wind deflection is grossly exaggerated to illustrate the point.

A bullet will move increasingly far offline [laterally] under the influence of a side wind (left panel, blue line). The lateral displacement is a curve, and this is why wind deflection at increasing distance is not simply additive (i.e. a straight line off to one side).

If the effect of wind stops at some point along the trajectory as shown in the right panel, let's say because there's a wall, or thick line of trees, the bullet will continue offline along the tangent line to the curve it had been traveling under the influence of the wind (red line). It will not return to some perfectly straight trajectory perfectly perpendicular to the target as it would have if there was no wind at all to begin with. It won't. It will continue to move further offline at an angle to the [straight] line of sight unless acted upon by some additional lateral force. It will not be displaced as far offline as it would if the wind continued for its full flight, but it won't go back to the original [straight] trajectory (perpendicular to the target face), either.

 

[Eagle Six]

Let's say it's 300 to the target and in the scenario in post 27, I weighted it to where the first 100 yards is SAME VALUE as the last 200 yards...iow, the drift from the muzzle to 100 should be equal to the drift from 100 to 300. This scenario should yield a dead on hold. Make sense now?

I think I have this correct, in simplistic terms using straight lines.....



From the muzzle at 2750 fps 10 mph direct cross R to L would be .41". From 100 yards at C with a velocity of 2638 fps 200 yards to the target line with a 10 mph L to R wind the drift would be 1.92". If we round those up to .5" left then 2" right, the bullet would drift back 4 times more from the left in the remaining 200 yards.

If I'm wrong oh well, if I'm correct this is a whole lot more than the thread was intended for even trying to keep it simple. If we consider that the wind (air) is both a gas and a fluid and can also have particle matter, and the earth is moving, and the bullet is spinning, I think my head is spinning, but regardless this straight line is most likely going to mislead rather than simplify.

 

[dcali]

I think you're splitting a fine hair. Be it a bullet or a weathervane, drag makes it move. A bullet will almost instantly turn and point INTO the wind regardless of which direction it spins or the direction of the wind. I'm not sure the rotational direction is enough of a factor to consider at this point of this discussion. Not saying it has zero effect but there are far bigger factors.

I think what he means is that the only reason a bullet turns into the wind is because it's spinning.

 

[dcali]

By the way, for anyone who is wanting to learn more about this, Bryan Litz's "Applied Ballistics for Long Range Shooting" is by far the best, most accessible source of ballistics info for non-engineers. Every long range competitor should have a copy.

 

[gunsandgunsmithing]

Here is a more visual representation of my previous statement. The trajectory due to wind deflection is grossly exaggerated to illustrate the point.

A bullet will move increasingly far offline [laterally] under the influence of a side wind (left panel, blue line). The lateral displacement is a curve, and this is why wind deflection at increasing distance is not simply additive (i.e. a straight line off to one side).

If the effect of wind stops at some point along the trajectory as shown in the right panel, let's say because there's a wall, or thick line of trees, the bullet will continue offline along the tangent line to the curve it had been traveling under the influence of the wind (red line). It will not return to some perfectly straight trajectory perfectly perpendicular to the target as it would have if there was no wind at all to begin with. It won't. It will continue to move further offline at an angle to the [straight] line of sight unless acted upon by some additional lateral force. It will not be displaced as far offline as it would if the wind continued for its full flight, but it won't go back to the original [straight] trajectory (perpendicular to the target face), either.

View attachment 1462321

I can pretty much agree with your pictures and I mentioned curved trajectory in a previous post. Again, you're splitting a very fine hair in terms of where the bullet lands using a straight line for discussion purposes vs the curved line that you describe...and I agree with. Now calculate how much momentum a 10mph(14.6fps) crosswind imparts on a say 105 gr bullet traveling forward at 3000fps(muzzle) in what .3 of a second to 300, roughly? Then go ahead and tell me how much more a curved and more true trajectory deviates from a straight line used for simplicity and discussions sake..at the target.

This discussion was about which wind matters most, right. Again, you're splitting hairs, while correct, is essentially of no value to the overall discussion.

 

[Eagle Six]

@gunsandgunsmithing take the illustration that @Ned Ludd posting in #48, a third the way to the target flip the curve from left to right and you have a better and more simplistic illustration of what you are asking.

 

[gunsandgunsmithing]

@gunsandgunsmithing take the illustration that @Ned Ludd posting in #48, a third the way to the target flip the curve from left to right and you have a better and more simplistic illustration of what you are asking.

What am I asking? Lol!
I gave a hypothetical previously, that you said won't happen. But that's why it was a hypothetical. Wth? Its sole purpose is to draw a very general mental image. Not to spit short and curlies 12 ways.

Bottom line, a bullet moves because of drag. With no wind, there is essentially no lateral drag and the momentum is frigging near nil. That's all.

 

[Ned Ludd]

I can pretty much agree with your pictures and I mentioned curved trajectory in a previous post. Again, you're splitting a very fine hair in terms of where the bullet lands using a straight line for discussion purposes vs the curved line that you describe...and I agree with. Now calculate how much momentum a 10mph(14.6fps) crosswind imparts on a say 105 gr bullet traveling forward at 3000fps(muzzle) in what .3 of a second to 300, roughly? Then go ahead and tell me how much more a curved and more true trajectory deviates from a straight line used for simplicity and discussions sake..at the target.

This discussion was about which wind matters most, right. Again, you're splitting hairs, while correct, is essentially of no value to the overall discussion.

Actually, it's not splitting hairs, and it is of value to the discussion, because it is the explanantion for why near wind moves the bullet farther offline than far wind.

 

[dcali]

I can pretty much agree with your pictures and I mentioned curved trajectory in a previous post. Again, you're splitting a very fine hair in terms of where the bullet lands using a straight line for discussion purposes vs the curved line that you describe...and I agree with. Now calculate how much momentum a 10mph(14.6fps) crosswind imparts on a say 105 gr bullet traveling forward at 3000fps(muzzle) in what .3 of a second to 300, roughly? Then go ahead and tell me how much more a curved and more true trajectory deviates from a straight line used for simplicity and discussions sake..at the target.

This discussion was about which wind matters most, right. Again, you're splitting hairs, while correct, is essentially of no value to the overall discussion.

At long range, that curve (or lack of curve) matters quite a bit. I think it's always helpful to know why things happen. It's saved me a lot of time and money over the years.

 

[Eagle Six]

Would it be much trouble to draw the hypothetical scenario I presented in post 27 above, with line A to B included?? I think that will draw a reasonably close mental image...fwiw.

What am I asking? Lol!

Well, you did ask, but apparently I am interjecting more than you want into your illustration, so I will bail out of it.

Nonetheless, @Ned Ludd illustration simplifies wind drift effect.

 

[snert]

Wow, lot's of science here.

I go by how the wind ruffles the hair on my legs (summer) or moves the snow (winter). I send one then adapt

 

[gunsandgunsmithing]

Actually, it's not splitting hairs, and it is of value to the discussion, because it is the explanantion for why near wind moves the bullet farther offline than far wind.

Show us by how much or yes, I say it's splitting hairs in the context of this discussion. A ballistics program should make it pretty easy. Wonder how much curve they use.

 

[Bottom Fodder]

After reading all this next time I go shoot I may spend time trying to figure out where to put the crosshairs than actually shooting