Rookie Wind questions about drift velocity and changing wind conditions...

[headhunter1111]

In my humble opinion, wind causes the bullet to point into it, it does not push the bullet off course, the amount that this would affect the flight is determined by the timeframe it is pointing into the wind, spin stabilization will cause point forward flight once again once the projectile exits the turbulence, then is affected once again every time it enters such a turbulence, therefore, if it enters a windy area first that will cause it to point into the wind, it will return to a more point of aim oreinted direction once it exits as it will be like a weather vane (poor example, good visual) and point directly into the wind IE straight ahead. This dirction would be determined by the angle it exits the first gusty area. Therefore, you would need to determine length of the windy area, figure the MOA adjustment there, it would remain on this course without further drift until it hits the second windy area, TOF would once again come into play, the projectile would hit it at the same degree angle it exited the first area, meaning a different O'clock value possibly (only in extremely windy conditions would this even be enough of an issue to consider), it would begin to point in the opposite direction then. Meaning TOF in wind conditions once again comes into play. Reduced velocity increases TOF through wind but it will have less affect as the distance to target has now been shortened. It's basically doping three winds, the first being the most important as it affects it over a greater distance, a calm where the bullet will remain on the altered course and finally the final wind which affects it only a short distance but at a reduced velocity. Boy my head hurts from all that.... if it were me this is how I would dope it.... by the time you've done this conditions will have changed more than likely but it's an awesome question to mull over. Thanks for the mental work out bud.

 

[necchi]

I realize my analogies are far from a bullet, but sometimes ya need to put aside the calulator frame of mind and focus instead on the actual natural forces.
When wind forces stop, the drift from the wind is going to stop, quickly.
I still don't think a bullet will continue to move sideways when the sideways force is removed.
It's almost the same as trying to bend a bullets path by swinging the barrel, (from a popular movie), it's not going to happen. When the motion stops it's force is stopped.
Billiard ball analogy won't work, those are objects of equal mass.

 

[BoydAllen]

Head hunter,
How does your model work with the most wind sensitive bullet shape, the round ball? The net time you are out for a drive, at highway speed, stick your had out of the window. The pressure that you will feel will always be in the a direction opposite to that of the car, assuming otherwise calm conditions. When you forcibly move the axis of rotation of a gyroscope (that is spinning at full speed), does it remember its initial position? Correlation does not prove causation.

 

[headhunter1111]

I'm not saying it returns to original direction, it doesn't move further in the wrong direction. It stays on the path it was on when it left the first wind, it doesn't however follow the rule of squares as it is not being acted upon by the wind at that point.

 

[BoydAllen]

Ah, now I understand what you meant. I think that the "rule of squares" is only meant to point out a relationship that is approximate in a constant cross wind.

 

[Keith Glasscock]

I just got done reading "The Wind Book for Rifle Shooters" by Linda Miller and Keith Cunningham. They have covered your question in detail. At the same time, they show it in easy to understand examples. I'd recommend it - not a bad read.

I got mine from Amazon, it was about $19 and advertised here on Accurate Shooter...

 

[RonAKA]

I just got done reading "The Wind Book for Rifle Shooters" by Linda Miller and Keith Cunningham. They have covered your question in detail. At the same time, they show it in easy to understand examples. I'd recommend it - not a bad read.

What did you learn about a wind that exists for a segment of the trajectory path and not for other segments?

 

[Nomercy]

I'm not saying it returns to original direction, it doesn't move further in the wrong direction. It stays on the path it was on when it left the first wind, it doesn't however follow the rule of squares as it is not being acted upon by the wind at that point.

Actually, just for the record, a gyroscope actually WILL return to it's original orientation. It's a fun experiment, hold a bicycle front wheel axle with the wheel standing vertically between your hands, press it against a grinding wheel to give it high velocity, then sit down in an office chair. Then turn the wheel horizontally, the force will turn you in the chair. When you right the wheel, you'll feel the force stop. If you tilt it the other way, it will turn you the other direction. It's the EXACT reason why motorcycles "want" to stand up, and why we use gyroscopes to determine orientation for aviation. Regardless of external force, the gyroscope will always want to return itself to the orginal orientation.

Spinning objects follow a right hand force rule. If you wrapped the fingers of your right hand around the object in the direction of the spin, the stability force would be in the direction of your thumb.

An external force will temporarily divert the axis, but the gyroscope will always want to return. So technically, yes, if a bullet DOES get a tail-whip from a stiff side wind (not certain I believe one ever DOES get substantial whip), if the wind relieves, then the bullet will line back out to it's original orientation.

 

[Nomercy]

I just got done reading "The Wind Book for Rifle Shooters" by Linda Miller and Keith Cunningham. They have covered your question in detail. At the same time, they show it in easy to understand examples. I'd recommend it - not a bad read.

What did you learn about a wind that exists for a segment of the trajectory path and not for other segments?

Ditto?

 

[BoydAllen]

Your example is not valid. If , for example, your bullet travels 50 yards under the influence of a 10 mph crosswind, by the time that it reaches the far side, it is on a new heading that it will continue on through still air that follows. When I was a kid, I used to ride my 10 speed "no hands" if traffic was light in the neighborhood. After a turn I would continue riding without using my hands. After the force that caused the change in direction was removed the wheel did not return to its original heading, but was stable in its new orientation. A friend has made electronic wind flags, for short range Benchrest. Each flag measures the effective 90 degree cross wind force at its location, with a fixed flat panel mounted on a brass rod that has a strain gauge. If your theory was correct, the summary reading would give the far "flags" a greater percentage of the total reading, because the bullet's deceleration results in greater time of flight in each successive down wind segment. In fact, the opposite is the case, and in robust and inconsistent conditions, it does a good job, with the summary giving the greatest weight to the nearest flags. Come shoot some short range Benchrest, when the wind is blowing, and you will see that a given velocity on a near flag causes more bullet movement than the same velocity at a far flag.

 

[Nomercy]

Your example is not valid. If , for example, your bullet travels 50 yards under the influence of a 10 mph crosswind, by the time that it reaches the far side, it is on a new heading that it will continue on through still air that follows. When I was a kid, I used to ride my 10 speed "no hands" if traffic was light in the neighborhood. After a turn I would continue riding without using my hands. After the force that caused the change in direction was removed the wheel did not return to its original heading, but was stable in its new orientation.

The reference is still valid for the bullet. It's part of why a bullet can restabilize after the sound barrier "transition". The reason a kid on a 10 speed can turn without his hands is that the momentum of the wheel (4lbs out of a 150lb system) can't overcome friction NOR the momentum of the bike plus the kid. But the heavier the wheel and the faster it turns, the more angular momentum it will have, it takes a LOT of force to lean a sportbike over at 150mph, MUCH more force than at 50mph. The axle of your 10 speed wanted to be in the same PLANE, so when you take the turn, your bike leans, but when you right yourself, the frictive "scrub" of the tires eats the angular momentum of the lightweight wheel.

The gyroscopic "right hand rule" is why a rifled bullet is self-stablized. The rotation of the bullet self stabilizes it's mass around the axis of rotation.

However, that's not to say that a bullet, modified by a 10mph wind 50yrds long, would try to "reset itself" to it's original direction. It's more of a micro-scale force than a macro force. Despite the wind kicking it in the butt, the bullet will still remain in a stable spiral. The Wind is much like the 10speed, once the heading is changed, the micro-scale stablization force can't return it to it's same heading, but it can assure that it continues to fly tip forward. Kind of like a football pass getting slightly tipped, it will bobble pretty wildly at first, but then it'll SOMEWHAT stabilize back to a spiral (or at least a "lame duck" spiral) as it finishes it's flight.

Once the bullet is off path, the macroscopic wind forces dominate, but the micro-scale gyroscopic stabilization is still acting (tip forward, not keyholing).

 

[BoydAllen]

Yes

 

[headhunter1111]

Correct, it does right itself into a straight line again rather than a parabola style trajectory, that is wind drift (I'm not talkig about drop here obviously) it is on a parabola during the first stage of flight in the wind. For example, if it is a 10 mph cross wind that drifts it 4 inches at 200 yds where it encounters the still air then flies 200yds in still air then hits a windy stage that affects it in the opposite direction for the last 200 yds.
First it is in a parabola style flight path, it is moved 4 moa to the right, it hits still air continuing 4moa off course (in a straight line) which would be 16" now, on it's last jog it has slowed a bit so when it hits the final right to left wind, it is moved slightly over 4 moa perhaps, because of the reduced velocity. So lets just say it is moved 5moa BUT it is only 200yds of wind. Therefore it moves only 10" so it would move on a parabola again. SOOOO it is 4moa off course @ 400 ie 16" right. It is moved BACK to the left 10". if it was only the first wind it would be moved 4moa through still air and hit 24" right, however, it has been pushed 10" of this course. So it would hit 14" right @ 600. Go try this method out and see how you like it. That is the only sure way to test any one elses theory or method out.