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Thread: Ballistic Coefficient of JSB Exact \ Air Arms Fields

  1. #1
    Marksman
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    Default Ballistic Coefficient of JSB Exact \ Air Arms Fields

    Anyone concur that the actual BC of these pellets is close to 0.029 and not 0.019 as stated elsewhere and also in Chairgun? :thinkerg
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  2. #2
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    that much more efficient?
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  3. #3
    casper's Avatar casper
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    Guido how did you test?
    I did a test about 2 weeks ago. Velocity at muzzle 796ft/s JSB Exact 4,51 tested over 20m. Velocity 690ft/s BC=0,019. This was done without anything fitted to the barrel.
    With AS fitted over same distance and pellet but not the same day. Velocity 726ft/s BC=0,030. In both cases I used 10 pellets and worked on the average velocity to do the calculation.
    Urabus did you do a calculation on the change in BC you got.
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  4. #4
    Marksman
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    I did a POI drop at 50yds with a 20 yds zero and nothing on the barrel.
    Instead of the claimed +44 click elevation adjustment I had to only adjust +32 clicks.
    Entering this adjustment in Chairgun gave me 0.029 ....next time I will check velocity at 50m.
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  5. #5
    Marksman
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    just checked
    velocity at barrel 782fps
    velocity 21yds 702fps
    BC 0.024 ?

    Casper I think you need to measure the velocity at 20m with and without the goodie on the same day....

    Measuring at 50yds will be even better.
    <span class='smallblacktext'>[ Edited Sun Jan 15 2006, 08:59AM ]</span>
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  6. #6
    casper's Avatar casper
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    Did a three way test and calculated on Chairgun:
    Steyr 592ft/s 0,025
    S400 @ 120bar 775ft/s 0,021
    S400 @ 160bar 814ft/s 0,023
    If I use your velocities in Chairgun I get BC=0,025.
    What rifle did u use Guido?
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  7. #7
    Marksman
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    LG110
    just checked Chairgun again
    782fps at muzzle
    702fps at 21 yds
    BC is 0.022
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