How do you judge wind

[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.

Nope. It's because the faster the retained velocity, the more drag and drag moves the bullet. I'm done. You can have it however you want it.

 

[gunsandgunsmithing]

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.

Does the principle change for short range? Of course not.

 

[pdhntr]

Newton developed some really cool ideas on this stuff. They are called Laws.

Get a marble and a long flat table. Have someone start the marble rolling on the table and then take your finger and give the marble a little poke 90 degrees to the direction of its roll. From above watch the course of the marble. When you poked it you accelerated it in a direction.

That direction cannot change unless it is acted on by another force that is opposite the original, AND that force has to be enough to overcome the inertia of the marble at the time the force is applied.

Jim

 

[gunsandgunsmithing]

Newton developed some really cool ideas on this stuff. They are called Laws.

Get a marble and a long flat table. Have someone start the marble rolling on the table and then take your finger and give the marble a little poke 90 degrees to the direction of its roll. From above watch the course of the marble. When you poked it you accelerated it in a direction.

That direction cannot change unless it is acted on by another force that is opposite the original, AND that force has to be enough to overcome the inertia of the marble at the time the force is applied.

Jim

Agreed...this is more to the point I made early on.

 

[wjm1000]

All this discussion about wind but no mention of “buck”. Ya know, so and so bullet bucks the wind better than some other bullet. I’d really like someone to explain this bucking thing. Does the bullet lean into the wind to avoid being blown around? Is it related to busting? Like brush busting bullets that don’t change course after plowing through a thicket? Please shed some light!

Well, they do buck and they are very difficult to ride. But once you get a feel how they buck and are able to predict there movements, you can be very confident where you will end up.

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.

That's what I was referring to in the original post,

 

[Ned Ludd]

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.

I don't have to show you anything. If you want to see the output from a ballistics program, run it yourself. I've done it, and I know what the correct answer is, which is exactly what I stated. It's not splitting hairs, it's the physics of wind deflection. If you choose to believe otherwise, I don't really care.

 

[gunsandgunsmithing]

I don't have to show you anything. If you want to see the output from a ballistics program, run it yourself. I've done it, and I know what the correct answer is, which is exactly what I stated. It's not splitting hairs, it's the physics of wind deflection. If you choose to believe otherwise, I don't really care.

Can't generalize with some types I guess. I can do the math in my head. And yes, there is a small amount of drift after the wind stops. The math is pretty simple and like I've been saying all along...it's a lot less than a constant wind. And I don't care what you do or dont do. Suit yourself but you haven't offered any numbers, just talk and other people's graphics without specific values....oh, and your typical condescension

 

[Bottom Fodder]

So this topic is getting heated now, grap the popcorn and set back as listen

 

[dcali]

Ned's right.

The reason the wind deflection curves down range in constant wind is that the wind is causing it to accelerate sideways the entire way. It's accelerating more near the muzzle and less down range as the velocity bleeds off, but the cumulative wind deflection grows exponentially all the way to the target. In part because the sideways velocity is continuously increasing (because of the wind), and in part because the forward velocity is continuously decreasing (because of drag).

If you remove the wind half way down range, you remove the acceleration, but there's still going to be a sideways velocity that continues all the way to the target. Even a brief puff of wind at the muzzle will see increasing deflection the further you go down range even if there is no other wind. Contrast that with a brief puff of wind right before the bullet hits. There is no room and no time for that puff to do much of anything.

When you add up all these factors, it means the near wind matters more. If that's all you want to know, skip the two paragraphs you just read.

At the end of the day, it's high school physics. F = ma.

 

[Ned Ludd]

Can't generalize with some types I guess. I can do the math in my head. And yes, there is a small amount of drift after the wind stops. The math is pretty simple and like I've been saying all along...it's a lot less than a constant wind. And I don't care what you do or dont do. Suit yourself but you haven't offered any numbers, just talk and other people's graphics without specific values....oh, and your typical condescension

Sorry Mike, but it's your typical condescension. You were the one that claimed I was splitting hairs and off topic. I made no reference to you or your posts whatsoever until that point. You don't seem to be big enough to admit you're wrong, and your only defense is to attack the person that disagreed with you. Pretty sad, really. Why don't you just give a rest?

With respect to the topic, is the wind deflection for a constant, full-value wind at 1000 yd exactly twice that of the wind deflection at 500 yard? Of course not, and it would be ludicrous to think that it was. In fact, wind deflection at 1000 yd might typically be about 2.2 to 2.3 times greater at 1000 yd than it is at 500 yd. That's because wind deflection is not linear. Wait for it, it's a curve, just like I stated early on. The departure angle of the bullet from line of sight increases constantly with distance. Again, that's known as a curve. If the force that caused that departure from line of sight (i.e. wind) ceases at some distance, the bullet will continue traveling along the tangent line to that curve from the point the force ceased to affect it as it moved onward. In other words, whatever angle of departure from line of sight it had at the moment the wind ceased will be retained as it travels further. So it continues to move farther away from line of sight. It doesn't somehow magically begin moving parallel to the line of sight again.

 

[gunsandgunsmithing]

Sorry Mike, but it's your typical condescension. You were the one that claimed I was splitting hairs and off topic. I made no reference to you or your posts whatsoever until that point. You don't seem to be big enough to admit you're wrong, and your only defense is to attack the person that disagreed with you. Pretty sad, really. Why don't you just give a rest?

With respect to the topic, is the wind deflection for a constant, full-value wind at 1000 yd exactly twice that of the wind deflection at 500 yard? Of course not, and it would be ludicrous to think that it was. In fact, wind deflection at 1000 yd might typically be about 2.2 to 2.3 times greater at 1000 yd than it is at 500 yd. That's because wind deflection is not linear. Wait for it, it's a curve, just like I stated early on. The departure angle of the bullet from line of sight increases constantly with distance. Again, that's known as a curve. If the force that caused that departure from line of sight (i.e. wind) ceases at some distance, the bullet will continue traveling along the tangent line to that curve from the point the force ceased to affect it as it moved onward. In other words, whatever angle of departure from line of sight it had at the moment the wind ceased will be retained as it travels further. So it continues to move farther away from line of sight. It doesn't somehow magically begin moving parallel to the line of sight again.

Omg...you're picking and choosing rather than actually reading. Otherwise you'd know that I've agreed with you about the curve aspect. Once again, yes, you are correct but splitting a hair that is mostly irrelevant to my point...a generalization to simplify the most important aspects of drift, but not every aspect. Just stop it. I'm done with this back and forth childishness.

To others...
In my previous example, I used 300 yards and a 10mph wind for the 1st one third, or 0-100 yards.

If you have a tof of .1 seconds and a half inch of drift in the previously mentioned 10mph wind over those first 100 yards you can convert that to lateral velocity equal to 5in/second.

The remaining tof, from 100-300 yards in this example is say, .22 seconds to cover the 200 remaining yards with zero wind.

To get the lateral velocity, we just multiply 5 seconds by .22. This is 1.1 inches. Add the .5 we got during the 1st 100 yards and the lateral movement at 300 is only 1.6 inches. Not much compared to full wind for the entire bullet flight.

Pretty simple.

Who wants to calculate lateral velocity degradation over that .22 seconds? I might be able to guess.

 

[Konocti's Wigwam]

Lick my finger and hold it in the wind!

I wish I had a kestrel but don't. I have sailed for many years and can read the wind pretty well if there are objects blowing, like a flag or trees, I realize that is not always the case when hunting. A kestrel doesn't give you the wind at your target though, does it?

 

[dcali]

Lick my finger and hold it in the wind!

I wish I had a kestrel but don't. I have sailed for many years and can read the wind pretty well if there are objects blowing, like a flag or trees, I realize that is not always the case when hunting. A kestrel doesn't give you the wind at your target though, does it?

You can get a wind meter on amazon for like $15. Kestrels are stupidly overpriced in my view.

 

[JFrank]

Check the rules before bringing electronic devices to a Benchrest event.

 

[davidjoe]

Nope. It's because the faster the retained velocity, the more drag and drag moves the bullet. I'm done. You can have it however you want it.

But, wouldn’t that suggest that 300 Mag would drift further than a .308, though, with the same bullet in same wind?

Isn’t it possible to experience relatively more drag, but drift less? What comes to mind in the 300 / 308 example is that magnum needs a lot more energy, to achieve a little less drift, but it still does achieve a little less drift (more of its energy was lost to drag).

I’m asking on the premise that the rate of bullets’ deceleration over distance, itself, decreases, such that the velocity shed is a front end proposition. (The idea of always moving toward terminal velocity, forward, eventually straight downward, and then finally not changing at all, with V dependent on BC).

 

[Coyotefurharvester]

3" bullseye, 3" wide prairie dog, sleeping coyote head at 300 yards variable mph cross wind. Flat open ground, you are worried about drift at the muzzle, cold bore first shot must connect? Good luck.

 

[dcali]

But, wouldn’t that suggest that 300 Mag would drift further than a .308, though, with the same bullet in same wind?

Isn’t it possible to experience relatively more drag, but drift less? What comes to mind in the 300 / 308 example is that magnum needs a lot more energy, to achieve a little less drift, but it still does achieve a little less drift (more of its energy was lost to drag).

I’m asking on the premise that the rate of bullets’ deceleration over distance, itself, decreases, such that the velocity shed is a front end proposition. (The idea of always moving toward terminal velocity, forward, eventually straight downward, and then finally not changing at all, with V dependent on BC).

That's correct. In fact, it's the case most of the time given the same bullet. There's a tension between velocity and drag. The magnum's higher velocity will win out over the higher drag force. The higher force is acting over a shorter amount of time.

It's interesting to note that that's not automatically true (even if it is 99% of the time). Take the example of supersonic .22 LR. It will experience more wind deflection than subsonic ammo because the supersonic drag force is so much higher, and it's not that much faster than the subsonic. The extra drag turns out to more than cancel out the extra velocity. Subsonics are weird- the drag is very low. The kinetic energy of a subsonic .330 BLK barely drops at all over 300 yards, for example. It's a heavy bullet with a tiny drag force. But a 50 grain bullet out of a .22-250 will lose a massive amount of energy in the same distance because the bullet is light and the drag force is massive.

And yes, the velocity is shed much faster near the muzzle than near the target. That's why low drag bullets are so important for long range shooting - the drag reduction lasts all the way to the target. In bizarro theoretical world, the bullet will wind up in nearly vertical freefall at terminal velocity (which is pretty slow).

 

[dcali]

3" bullseye, 3" wide prairie dog, sleeping coyote head at 300 yards variable mph cross wind. Flat open ground, you are worried about drift at the muzzle, cold bore first shot must connect? Good luck.

Absolutely. I shoot a whole lot of 3" X rings at 600, and I will absolutely miss if I don't pay attention to wind at the firing line. 3" at 300? less so - that's a pretty generous target for a good rifle. But wind is wind. Watch it where it matters most.

 

[seymour fish]

This is exactly what a ballistics calculator will tell you. They're very helpful as learning tools. Less so at making real life wind predictions.

This entire discussion is 2-dimensional, in a three-dimensional world. No consideration is given to the delta wind speeds at various trajectory heights off the deck, thus are weighted inappropriately heavily towards wind at the muzzle.

 

[davidjoe]

It's interesting to note that that's not automatically true (even if it is 99% of the time). Take the example of supersonic .22 LR. It will experience more wind deflection than subsonic ammo because the supersonic drag force is so much higher, and it's not that much faster than the subsonic. The extra drag turns out to more than cancel out the extra velocity. Subsonics are weird- the drag is very low. The kinetic energy of a subsonic .330 BLK barely drops at all over 300 yards, for example. It's a heavy bullet with a tiny drag force. But a 50 grain bullet out of a .22-250 will lose a massive amount of energy in the same distance because the bullet is light and the drag force is massive.

It’s very interesting how this shape is so prevalently used, around .85 Mach.

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I’ve been finding better groups with an even flatter nose. (I can’t easily reconcile my approach in LR Fclass with my .22 game, that’s certain, and the one I put less thought into is going better.)