Velocity change with altitude

Discussion in 'Long Range Hunting & Shooting' started by 408w, Sep 15, 2019.


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  1. 408w

    408w Member

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    I have a kestrel so I can adj for altitude, but not a velocity change because of it on a hunting trip. How much is velocity effected by elevation? 300 win mag at 2850fps with a 200g bullet. 3000ft difference in altitude. FPS change? At 1800ft elevation here where I shoot. Am I over thinking it?
     
  2. AZShooter

    AZShooter Well-Known Member

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    The velocity at the muzzle should be the same at different elevations unless temperature is a factor with your powder.

    Down range performance including velocity will change with altitude but sometimes lower temperatures accompany higher elevations causing a cancelling out so performance and velocity could remain close to what you had at the lower elevation and higher temperatures.

    Crunch some numbers and compare.
     
  3. 408w

    408w Member

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    Thanks
     
  4. mudygmc

    mudygmc Well-Known Member

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    Download a ballistic app. Strelok is free and what I use. Been very accurate for most everything ive tried in it. Like AZshooter said. Muzzle velocity should be virtually the same. Pressure and temp will most likely be the different factors that will effect down range velocity.

    Adam
     
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  5. Thescandinavian

    Thescandinavian Active Member

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    Elevation won't change velocities.
    Different air density will change velocity.
    If you calibrate a barometer you do so to keep within the standards. If you get the barometric pressure of a online source you would calculate the difference in elevation, if having a handhold device I would just use the pressure it's calibrated for at sea level without change for elevation. Am I wrong?
     
  6. jebel

    jebel Well-Known Member

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    This exactly.

    You could shoot in deep space and the muzzle velocity would be the same, powder temp accepted. Those are internal ballistics.

    You’re thinking about external ballistics, the stuff that happens after the bullet departs the muzzle.

    Your ballistics app and kestral will certainly come into play with differing external conditions, but they don’t have any bearing on internal ballistics (again, powder temp accepted).

    Remember, it’s internal, external, and terminal ballistics. We have great, accessible data on external, somewhat less on internal, and a mess of poor data and multiple unsubstantiated theories on terminal.
     
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  7. Jeffrey Van Zandt

    Jeffrey Van Zandt Well-Known Member

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    if you have the Kestrel 5700 it is not elevation but DA temp can also be build in to the kestrel for your powder if you have trued it to your round at the right range it will give you the right scope setting but it is only going to work right if you have put in thee right dope
     
  8. JarHeadTim

    JarHeadTim Member

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    Check your messages
     
  9. DavidleeCole

    DavidleeCole Well-Known Member

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    Air density has a great effect on bullet drop as the closer to sea level the harder it is for the bullet to push through the air and wind. Adversely the higher up the mountain you go the less dense the air is and its easier for the bullet to push through. With my 300 Whby mag at 500 yards going from 95 degrees at 450 feet elevation and 29.5 inhg my drop is 1.1 mil and going to 50 degrees at 6000 feet and 24.0 inhg my drop is 1.0 mil a little over 2 inches. As stated in an earlier post it's not that much. However when you take into vertical dispersion due to velocity variations from extreme spread and your systems group size and the size of target you may slip outside the vital zone. Some medium game is around 7 inches and large game around 10 inches. For me I like to take in everything I can to get as accurate fire solution as possible. So I should be the limiting factor not my system.
     
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