Humble pie... and the wind...

Discussion in 'Hunter (HFT) & Field Target (FT)' started by RobF, Apr 26, 2011.

  1. RobF

    RobF Administrator Staff Member

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    Grief, it's hard to type this thread starter....

    For years I have denied that pellets move up and down in the breeze... because there's been very good more likely reasons why that should happen when i've seen it happen...but after yesterday I am willing to admit they might move... still not convinced they may move as much as some thing, or that it's the sole reason that people shoot high or low, which I think is largely range/shift driven.

    Yesterday we had a strong breeze coming right down the throat of South Dorset's plinking range. When it swung left it took 6" off me at 55yds, which in my book puts it about 20 mph... it was strong enough that the windy was horizontal and could buffet you a tad.

    We started shooting at 55, and had good consistent groupings, pellet on pellet at 55, but now and then the shots would fly 1/2 MOA up, or 1/2 MOA down... and group there. In the end, I elected to only shoot when the wind was soft and consistent and the shots stayed level. Looking at the trend, left was lower by about 1-2 clicks, right higher by 1-2, mostly both in the 1 click range. Off the bench it meant that I was less likely the weak link.

    What sort of nailed it for me was that even though my windy was pointing strong left, a lot of shots would go straight, but low... but when the windy was pointing straight down, they would go straight but be on the level... there weren't many taken when it was pointing right that went straight, but they did climb a click.

    Shots that went left when the windy pointed left didn't drop as much as those that were fired when the windy pointed left but went straight. The groups I was getting were tight, but just seperated by 1/2 MOA. Only when I shot in consistent wind did I get a consistent group.

    The feeling was that when shots are going left, they may go a little low, and that when they go right, they may go a little high... but we are only talking 1/4 MOA... but the real damage seemed to be when a really strong wind pushed them back on central line.

    So I think that perhaps when the wind is super strong, you may see some lift and drop depending on what it's doing, but we are talking very strong wind, and still marginal amounts, and I still reckon on most occasions it's going to be down to rangefinding or shift errors, and you need to dial out pellets first.

    Need to investigate more, and stick a chrono at 55 on a windless day and see what happens then for a comparison... couldn't be arsed to stick the chrono out yesterday as I lacked the tripod... and besides, the occasional horizontal drift would have been well enough to clip the sensors...

    Chairgun says it should happen, but not to the same degree... but then it says that about a lot of things, and i've found it's findings to be right in direction, but less than what seems to happen in the real world.

    What would be great is to be able to get two CED M2 IR's together one day, tie them so they are reading the same and do some BC work as well, cos I have a new theory as to why sizing might reduce vertical spread on pellets.
     
  2. Miss England

    Miss England Mr. Kipling has nothing on me

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    How does that Humble Pie taste.... ;) :p

    You manged to post before I could tell the world that what you swore never to happen actually did!!!!

    I have to admit that I never really believed that the wind would move a pellet up or down as you never really get a wind that blows directly downwards or upwards, but that indeed was exactly what happened.... very frustraiting when you are trying to do your ranges........ :p

    Although if did effect the flight of the pellet the movement was so minimal that it would not really have an impact on making the shot... unless you were doing a 15mm kill at 55 yards...... but there was definatly wind assisted movement.....

    We saw 1 click of movement both up and down (at one point I had 2 neat lines above and below the actual aim point, then when the wind dropped I could get the middle line.....) 1 click being a pellet width at 55 yards.... so minimal effect and this lessened with shortened distance......

    Mind you the sideways movement was just as errattic, sometimes taking the pellet 6 inches other times it was spot on and if you were quick enough to get another shot off before the wind started again it was pellet on pellet.....
     
  3. njr74

    njr74 New Member

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    i hope you to haven't been teaching my spare gun bad habits? ;)
     
  4. neilL

    neilL New Member

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    I saw a few go left and low even though I was in a comfortable position and well within ranging comfort. It was almost as if the side gust slapped the pellet (gap in the bushes?). Chairgun is useful for seeing what parameters make a bigger difference, scope height is a big one but that shouldn't change! Pellet speed is not very sensitive it seems, assuming the regulator lives up to its name. BC is, rightly, a bigee and any time I see numbers quoted to 8 decimal places (hover the mouse over the BC box) it bothers me (I used to be a 'scientist' and did my A-levels and degree using a slide rule and 4-figure log tables! - good enough for NASA engineers hahaha).

    BC is a mish-mash of a lot of variables and is possibly best described as a fudge-factor for air rifle pellets (bigger, better defined bullets are likely to be more consistent). What we really need is a fancy 3D laser measuring rig which gives some real numbers for the dimensions, weigh it to some reproducible standard (balance vs. a standard) and then bench test it indoors with a couple or more chronos. Failing that a couple of nice soft touch micrometer gauges.

    I suspect you are right and that will eventually give you some multi-variate headache but a better understanding of what measurement is the one to go after or maybe two.

    It would be a lot of fun to do that and then have some smoke streamer (wind tunnel like things) outdoors to show exactly what is blowing and which way or even decent wind meters and then put theory to test.

    If I can help with a marathon day of measuring, weighing and testing let me know.

    Alternatively we throw people who get 46+ on such days in to the fish ponds - if they float then they are witches.. :)

    Cheers
    Neil
     
  5. PeteM

    PeteM New Member

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    Sounds like the Magnus Effect somehow...!
     
  6. holly

    holly Well-Known Member

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    Fact ?

    Try this . find a good thick hedge , with the wind coming straight over it toward you . put a target in front of the hedge and one above it and behind it . the one in front should strike low the one above and behind should strike high . there is a bank on the wstern side of west london rangers . it is quite famous for pushing pellets down . you always had to aim top of kill at the least ??? HOLLY
     
  7. Dale

    Dale Active Member

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    :D Glad you felt up to admitting to this.

    I long ago became convinced that there is an effect to the vertical POI as a result of strong winds. I found this out when Cornwall FTC was based on an old mine site on a 600 foot hill with line of sight to both the Atlantic and the English Channel. The firing points were reasonably sheltered but downrange was open to the full effect of the wind.

    Finding the pellets being pushed up an down as well as laterally was not unusual.
     
  8. RobF

    RobF Administrator Staff Member

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    slight rewind... we think it could have been the pellets... we saw the same behaviour on another range in light wind... switched the tin and it dissapeared, went back to the old one, and it appeared...
     
  9. NJR 100

    NJR 100 Because I`m AWESIME !!

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    Mozzies???

    Which batch were moving up down, which not?
     
  10. chrispro97

    chrispro97 New Member

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    are these happening with mozzies rob
     
  11. RobF

    RobF Administrator Staff Member

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    same batch of mozzies, an 2005 lot... changed tin, all good again... and they all looked good... tested in 2 walthers as well, weighing and sizing helped, but it still wasn't as good as another batch.

    might look into lubing...
     
  12. Adam

    Adam Active Member

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    I can't say that this effect couldn't happen, Magnus effect or whatever, but how could anyone rule out the effect of wind eddies pushing the pellet up and down slightly? How could anyone be certain the airflow at that instant was totally horizontal? The air will be travelling slower at ground level than it is higher up. Even in a constant horizontal wind, this will create eddies where the faster air meets the slower air. If the ground was 100% flat and polished smooth this might be minimised, but eddies must be present on any outdoor range with grass or bushes or whatever.

    I can't start worrying about a click up or down until I can consistently estimate how much left/right to give it, especially after last weekend! :eek:
     
  13. JAGXKRS

    JAGXKRS Sparky's Bodyguard

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    Rob if you don't believe pellets can move up and down in the wind come and shoot at Quarry sometime, you will change your mind;):eek:
     

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