Sighting in at sea level and hunting high

Discussion in 'Long Range Hunting & Shooting' started by Billinsd, Aug 11, 2009.

  1. Billinsd

    Billinsd Well-Known Member

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    If I sight my 7mm Rem Mag at sea level and at 70 degrees F and zero it at 100 yards, how high will I hit at 11,000 feet and 40 degrees F at 100 yards?

    Seems like not much?

    I have a Leupold VX II, 3x9 and had their custom shop install an elevation turret, specifically for the ammo I'm going to use on the hunt and the expected conditions.

    It's not practical to sight the rifle in at 11,000 on my trip and probably not practical to sight it in near the camp.

    How far off would I be, assuming I zero the gun at 100 yards at sea level and the gun, scope, mounts and rings do not get jarred while I get up to 11,000 feet and take a 100 yard shot? A tenth of an inch or so?

    Really, my concern is how far off I would be further down range, because however much off I am at 100 yards will get magnifed further down range.

    I'm planning to take shots out to 600 yards, which is what I am comfortable doing with lots of practice.

    Thanks in advance
    Bill
     
    Last edited: Aug 11, 2009
  2. elkaholic

    elkaholic Well-Known Member

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    Let's say you are using a 168 berger which has a high b.c. and your mv is 3200 fps. Not taking into account any other variables, you would have just over 5" higher impact at 600 yds.........Rich
    At 100 yds the impact would be insignificant.
     

  3. ATH

    ATH Well-Known Member

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    This is not an exact answer, but....

    When I compared sighting in at 300ft in warm weather and hunting at 8000 ft in cool weather, I found that once I compensated for atmospheric pressure (hit higher), cooler temp (hit lower), I came out relatively close to the same numbers. When I test-fired upon getting to altitude I found my calculations to be almost exact.

    You're another 3000ft up, so the difference should be greater. But on elk-sized game, if you are within 5 inches on drop, you should be ok.
     
  4. kiwi3006

    kiwi3006 Well-Known Member

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    If you go to the JBM webpage and download the Al_Bal program it has a function that will give you an idea.

    Set up the conditions you sighted in under with the box "Muzzle Angle Correction for Zero Range" box ticked.

    Then run the range table box.

    Then untick the "Muzzle Angle Correction for Zero Range" box and change to the conditions that you will be hunting under.

    Then run the range table box.

    This should give a good idea of the difference between the two.

    7mm Rem Mag at sea level and at 70 degrees F and zero it at 100 yards,
    100 yds +0.00 600 yds -10.54 MOA
    how high will I hit at 11,000 feet and 40 degrees F at 100 yards?
    100 yds +0.02 600yds -9.50 MOA

    Stu.
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    As stated already, your LR impacts will change. Your raw 100 yard zero wont change enough to talk about.
     
  6. Billinsd

    Billinsd Well-Known Member

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    Thanks, looks like I have nothing to worry about, since I got a custom turret for 11,000 feet, 45 degrees, and for the ammo I will use.

    Thanks
    Bill