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Wind drift

woodchuckjohnwoodchuckjohn Member Posts: 207 ✭✭✭
edited April 2014 in Ask the Experts
Having a problem with wind, something I have not payed much attention to in the past. My 204 ruger is sighted in at one inch high at 100 yards, dead on at 200, 4 inches low at 300. Is there a rule of thumb concerning hold over left or right based on MPH of wind. I have read one man say it is 2.5 inches per 5 MPH of wind. Any thoughts?

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    Ray BRay B Member Posts: 11,822
    edited November -1
    As the BC of your bullet decreases the "grip" of the wind on your bullet increases. Most bullets for a .20 caliber have pretty low BCs. As such the affects of the wind will be more noticeable than a standard guideline.
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    Hawk CarseHawk Carse Member Posts: 4,373 ✭✭✭
    edited November -1
    Feed your ballistics - actual muzzle velocity and ballistic coefficient - into one of the trajectory calculators and it will show wind effects. I use JBM
    http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
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    Mod1892Mod1892 Member Posts: 120 ✭✭
    edited November -1
    Here is another ballistic calculator I use. It is very helpful
    http://www.winchester.com/learning-center/ballistics-calculator/Pages/ballistics-calculator.aspx

    Michael

    Model 1892 / 61 Collector, Research, Valuation
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    tsr1965tsr1965 Member Posts: 8,682 ✭✭
    edited November -1
    The many ballistic calculators, will give you an idea of what you are up against. You can also get a wind meter to tell you what the wind direction, and value is at the point you are standing. However that information only covers the range at which you are standing, and not the entire range of which your fired projectile will traverse. That is part of the fun, learning to dope the wind. Being able to read signs, like tall grass, small tree's, leaves, deflection, to give you an overall idea of the total wind.

    This something that takes practice, in being able to do consistently. Practice, takes time, and money, for mounting ammunition cost.

    As mentioned previously, in another post, the smaller the bullet, the more they are effected by the wind. 17's, 20's, and even 22's are especially vulnerable to the wind. The first real good bore diameter that has better capabilities, would be the heavy 6mm's, and even better, the 6.5mm's. The further up the scale, the better it gets. While the smaller calibers are awesome on windless days, they do cause frustration, with even small amounts of wind.



    Best

    EDIT 1

    quote:

    The caliber (diameter) and weight of the bullet has nothing to do with wind deflection. It is all in the BC and velocity.


    When reverting to conventionally constructed projectiles, made of lead alloy core, with a copper guilding metal jacket, the caliber, and weight most certainly do have an effect on the ballistic coefficient, as well as does the projectile's design. Outside of conventional, if the construction is the same...plastic, wood, aluminum, etc. Who ever told you that, has misinformed you.

    Monolithic projectiles of the same caliber(read as solid copper projectiles with no lead core), weight, and design, are usually in possession of a higher ballistic coefficient than their conventional designed counter parts.

    Weight does in fact have a part in wind deflection, in itself, as the principal of momentum is in play, the very moment the projectile leaves the barrel. A brick, and a sponge of the same identical dimensions, are launched at the same velocity, with a 20MPH cross wind...which one will it blow the furthest off course, at 100 feet?...Yes, I thought so.

    The "Physics" that you are referring to, are the laws of GRAVITY.

    Best
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    CheechakoCheechako Member Posts: 563 ✭✭✭✭
    edited November -1
    The caliber (diameter) and weight of the bullet has nothing to do with wind deflection. It is all in the BC and velocity. Two bullets with the same BC at the same velocity will have the same ballistics. It doesn't matter if one is a 500 grain .458 and the other is a 60 grain .224.

    Do the math and you'll see. It's simple physics.

    Ray
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    CheechakoCheechako Member Posts: 563 ✭✭✭✭
    edited November -1
    tsr

    You are twisting my words.

    If you'll go back and read my post, I said that the only two factors are BC and velocity. Yes, the caliber, weight, and shape do determine the BC, but I never said that they didn't.

    If a brick and a sponge had the same BC and velocity they would be equally deflected. The old saw about the feather and the brick falling to earth is simplistic and doesn't really apply to ballistics. You can prove the fallacy of old wives tales like that by conducting the experiments in a vacuum.

    Bullets are not blown off course, as you put it. They are deflected. The bullet's nose will turn to follow the wind. The cross sectional area of a bullet has nothing to do with it.

    Gravity is but one of the laws of physics, not the only one. It plays a role in the trajectory of a bullet, obviously, but very little in the effects from wind.

    With all due respect, whoever told you all of this bunk has misinformed you. There are several free ballistic programs on the internet. Plug in all the data and see what results you get. They will surprise you. Both external and internal ballistics are governed by simple physics. You can't bend or break the laws of Mother Nature no matter how much you may think they are wrong.

    Ray
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    mcasomcaso Member Posts: 1,120 ✭✭✭✭✭
    edited November -1
    AND NOW TO ANSWER THE QUESTION of, any thoughts on aiming 2.5 inches to the right or left per 5mph of wind with a 204 Ruger at a distance 100 yards, please.
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    babunbabun Member Posts: 11,054 ✭✭✭
    edited November -1
    quote:Originally posted by Cheechako
    tsr

    You are twisting my words.

    If you'll go back and read my post, I said that the only two factors are BC and velocity. Yes, the caliber, weight, and shape do determine the BC, but I never said that they didn't.

    If a brick and a sponge had the same BC and velocity they would be equally deflected. The old saw about the feather and the brick falling to earth is simplistic and doesn't really apply to ballistics. You can prove the fallacy of old wives tales like that by conducting the experiments in a vacuum.

    Bullets are not blown off course, as you put it. They are deflected. The bullet's nose will turn to follow the wind. The cross sectional area of a bullet has nothing to do with it.

    Gravity is but one of the laws of physics, not the only one. It plays a role in the trajectory of a bullet, obviously, but very little in the effects from wind.

    With all due respect, whoever told you all of this bunk has misinformed you. There are several free ballistic programs on the internet. Plug in all the data and see what results you get. They will surprise you. Both external and internal ballistics are governed by simple physics. You can't bend or break the laws of Mother Nature no matter how much you may think they are wrong.

    Ray


    +1

    Wind affects a moving object {bullet} differently than a stationary, say, a skyscraper building.
    Here is a quote from a study of external ballistics.
    ""Wind has a range of effects, the first being the effect of making the bullet deviate to the side. From a scientific perspective, the "wind pushing on the side of the bullet" is not what causes wind drift. What causes wind drift is drag. Drag makes the bullet turn into the wind, keeping the centre of air pressure on its nose. This causes the nose to be cocked (from your perspective) into the wind, the base is cocked (from your perspective) "downwind." So, (again from your perspective), the drag is pushing the bullet downwind making bullets follow the wind.

    A somewhat less obvious effect is caused by head or tailwinds. A headwind will slightly increase the relative velocity of the projectile, and increase drag and the corresponding drop. A tailwind will reduce the drag and the bullet drop. In the real world pure head or tailwinds are rare, since wind seldom is constant in force and direction and normally interacts with the terrain it is blowing over. This often makes ultra long range shooting in head or tailwind conditions difficult.""
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    tsr1965tsr1965 Member Posts: 8,682 ✭✭
    edited November -1
    Ray...OK...I'm not going to argue with you, as it does nothing for the original poster. In his case, which you failed to address, there is nothing that can properly dope the changing wind conditions, other than learning how to read the wind. My original post was to show the shooter that the higher BC bullets(yes, usually the smaller bores have smaller BC's...agreed?) do in fact defy gravity better, as well as fight the wind better.

    Do you disagree with that? Is it OK to post that? Or are you just going to post to pick a fight?

    Best

    PS...While you are looking this over, check out the link in my signature, and see if there is anything that you may like.
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    CheechakoCheechako Member Posts: 563 ✭✭✭✭
    edited November -1
    tsr

    Read babun's post. He explains it a lot better than I did.

    And, do what I suggested. Run a couple of exterior ballistic tables, changing the different input, except for BC and velocity, and see what you come up with. It will probably surprise you, and you may learn something in the process.

    Ray
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    tsr1965tsr1965 Member Posts: 8,682 ✭✭
    edited November -1
    quote:Originally posted by Cheechako
    tsr

    Read babun's post. He explains it a lot better than I did.

    And, do what I suggested. Run a couple of exterior ballistic tables, changing the different input, except for BC and velocity, and see what you come up with. It will probably surprise you, and you may learn something in the process.

    Ray


    Ray,

    I am actually starting to like our conversations, and learn from them...hard headed as I may be. I did just do that what you said, and it does come out the same in theory. I have something haunting me in the back of my mind(I know...what mind, right?), as to an event a few years back. Got into an informal shooting match...,I had two rifles there, my 243 loaded with 55 grain ballistic tips, and they were leaving about 4000fps. The other rifle a 1874 Quigley sharps, in 45-70, running a 405 hardcast about 1400 fps. The day itself was beautiful, except for the wind, sometimes gusting to 30mph. The game we were playing in this one round was shoot the clay off the nail at 200 from the bench. It came down to a shoot off, between myself and one other gent, and he was using a 300 win mag. I tested the two rifles I had, and the 243 was wind deflecting 5 inches at 200 yards, and the 45-70 was about half of that...I used the 45-70 for the whole match, and did win the shoot off.

    Now I know that the velocities and BC's were not the same, for sure, and the very instant I fired them to test them was not the same exact wind conditions for both...but that is just something that sticks in my head, about momentum.

    If you wish to talk more about this, I would love to, but please PM me, so we don't have to bore these other folks.

    Tim
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