Crosswind effects on Vertical

Discussion in 'ELR, Ballistics & Bullets Board' started by xswanted, Feb 12, 2019.

  1. xswanted

    xswanted Gold $$ Contributor

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    Hi guys,

    In StrelokPro you can choose to use vertical deflection from wind drift or not use it.

    It looks like it changes things a bit in some cases and quite a bit in others, depending upon distance to the target of course.

    The question is......If a guy was shooting at a smaller target, let’s say a 6” circle out to 600 yards, how much would you rely on using the vertical deflection vs not?

    Would you base it on how windy it is?

    Or is it not worth worrying about inside of those distances?
     
    Last edited: Feb 12, 2019
  2. SPJ

    SPJ Silver $$ Contributor

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    I don't use strelokpro, but I do understand spin drift and vertical deflection so I would vote to use any and all tools at my disposal
     
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  3. Meangreen

    Meangreen

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    The vertical offset amounts to about 10% of the drift.

    Assuming a right hand twist, a wind from left adds to overall drop, while a wind from the right subtracts from overall drop.
     
  4. xswanted

    xswanted Gold $$ Contributor

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    That’s a pretty good explanation in simple terms of how to figure this out.

    Thank you.
     
  5. xswanted

    xswanted Gold $$ Contributor

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    It loooks like by just running some scenarios in the app.....

    Using a 14mph crosswind at 600 yards, assuming a center hold on a 6” target one would miss if your not using the crosswind deflection.

    Using an 8 mph wind it looks like one would hit in the same scenario not using the deflection.

    I think I’ve answered my own question by doing this, but the crosswind deflection is certainly looking to be beneficial.
     
  6. Falfan2017

    Falfan2017 Gold $$ Contributor

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    It definitely matters. Had a light crosswind like 7 mph left to right at an f class match on Saturday. When it picked up to 12 or so it was enough to almost push a bullet low out of the 10 ring if using a center hold. Had to hold on the top left side of the 10 ring to get it back in the x. This was at 1000 but still 600 is far enough to matter.
     
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  7. chkunz

    chkunz Gold $$ Contributor

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    Shooting smallbore prone at 100 yards will give some good experience with this phenomenon.
     
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  8. Eternal Student

    Eternal Student

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    That's it? 10% of SD? I could see the importance on longer shots but where do you draw the line between not the best wind call/or last sec. change in wind and vertical jump?
     
  9. Milo 2.0

    Milo 2.0 Gold $$ Contributor

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    I'd use it for sure. Build some different profiles in the app. I think you'll see lesser bc bullets that are affected more by spin drift in the wind will drop more too.
     
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  10. xswanted

    xswanted Gold $$ Contributor

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    I’ve been using it on the phone app, but I made some cards for rifles I coyote hunt with. Those are more for quick reference so I left it off for those as i won’t know the wind until I’m sitting there.

    If I have time to use the app for a long coyote shot I think I still will but otherwise use the cards

    I shot at 835 yards last Sunday and it was significant with the wind and conditions I had as far as elevation was concerned.

    Very interesting for sure.

    Thank you!
     
  11. Milo 2.0

    Milo 2.0 Gold $$ Contributor

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    Until I got a phone app which does it automatically, I held high left on top of wind hold with left wind, low right with right wind, right tw barrel. Seemed to work.
     
  12. Meangreen

    Meangreen

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    10% of wind drift, not spin drift. A 2 mil wind call would mean 0.2 mil vertical effect.
     
  13. Ballisticboy

    Ballisticboy

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    The vertical effect of a cross wind is caused by the gyroscopic effect of the bullet yawing to face the relative air flow produced by the combination of the bullet speed and the wind speed when it leaves the gun barrel. When the bullet yaws slightly left or right the gyroscopic reaction is to make the bullet yaw up or down depending on the wind and spin direction. It is not a Magnus effect since, as the bullet yaws to face the relative air flow, there is no air flow across the bullet.
    The percentage of the vertical change compared to the down wind drift will change with range and bullet configuration. This is because the vertical effect is a linear change with range governed by the bullet aerodynamic and inertial properties whereas the down wind drift is closer to exponential, however as both will be affected by the velocity drop, it is not going to be quite that simple.
    It is a real effect (some people try to claim it does not exist) and has lead to major challenges in the past for some projects. It is not a function of gyroscopic stability but it is dependent on many similar bullet properties so the two do tend to be related.
     
  14. Meangreen

    Meangreen

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    Nobody asked that.

    Uhmm...what?

    You are talking about the number of fairies dancing on the head of a pin. We're not calculating a moon shot. According to Bryan Litz...it's about 10% of wind drift.
     
  15. HuskerP7M8

    HuskerP7M8

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    I read a lot here but post rarely, and I truly appreciate every one of "Ballisticsboy's" contributions.

    In my estimation he's the most knowledgeable ballistician that deems to post over the great many years I've followed the subject on more forums than I can count.
    He's the real deal and not a self-taught amateur ballistician like myself or the rest of you.

    You guys seem to have no idea how fortunate you are that he has decided to post every once in a while and help us understand a very complex science.

    Every single thing he said in his post is correct in my opinion, and anyone who doesn't understand it should continue to do more research.

    Landy
     
  16. Meangreen

    Meangreen

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    Engineer types...to include ballisticians, quite often miss the forest for the trees.

    I have several in my close circle of friends. They could write an equation for catching a baseball while wearing the glove on the wrong hand.

    I like smart numbers guys, we need them. I'm not about to cut them any slack though.
     
  17. Milo 2.0

    Milo 2.0 Gold $$ Contributor

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    Almost all BB prints, along with Litz, is basically over my pay grade. More that I choose not to go that deep. In real world applications does it matter if your bullet yips, yaws, or yells all the way to the target? It is rare any of us need to cold bore a pinpoint shot. You can understand and know wind and terrain patterns and predict where your bullet is going to go w/o understanding gyroscopic rotations of a bullet..
    If you are shooting 1K benchrest, a couple sighters reveal your best laid plans aren't going to work. Make an adjustment, and when the timer beeps, go to town.
    If you are wagering 10K on one shot at a prairie dog at 1200 yards, you either have too much money or too little upstairs
     
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  18. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    And many non-engineer types often miss the trees because they are in the middle of a forest. Rote memorization of numbers is great once you have a more thorough and detailed understanding of a topic or principle, otherwise, you end up with a bunch of ignorant shooters that memorized some numbers, but have no idea what any of them actually mean. I am another member that appreciates Ballisticboy's detailed explanations. I can read his responses and decide for myself what information to retain or cull. If the information isn't there to begin with, I lose that choice. This is a shooting forum where a wide variety of opinions and responses are to be expected.
     
  19. Meangreen

    Meangreen

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    Yep. But I don't think you like mine very much.
     
  20. damoncali

    damoncali Gold $$ Contributor

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    If you were to ask Bryan, he’d tell you exactly what Ballisticboy, who knows a thing or two, said. 10% is a very rough number, to the point of being misleading in some situations. Jump as a percentage of windage is not a constant. It changes with range.

    Knowing that does not require an engineering degree- only that you listen to someone who has figured it out and tested it.

    To the op, practically speaking, you don’t have to worry about it at 600 and 1MOA targets unless you’re seeing highly variable, strong cross winds at the firing line, or you’re trying to make a first round hit in a strong cross wind.
     
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