setting up long range gun

Discussion in 'Long Range Hunting & Shooting' started by bcoving, Jul 16, 2009.

  1. bcoving

    bcoving Well-Known Member

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    I'm just learning about long range shooting. Can someone explain to me their process for setting a gun up. What I'm confused on is after load developement what is your process. The way I understand it you need to shoot your gun at each distance then change the BC in the ballistics software to make the drop charts line up with the actual MOA drops that your gun had for each distance? Can someone explain from start to finish how they would set a new custom gun and new scope up for long range shooting.
     
  2. MontanaRifleman

    MontanaRifleman Well-Known Member

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    The two big question marks in determining your trajectory are velocity and BC. Most manufacturer BC's are questionable. Bryan Litz has done some great work testing the BC's of various bullets and has published a book which will probably answer a lot of your questions.

    http://www.longrangehunting.com/forums/f19/new-book-applied-ballistics-long-range-shooting-43573/

    His data has also been imported to the JBM online ballistics calc.

    JBM - Calculations

    This site also has a function for detrmining BC through differential velocites.

    Most BC's use the G1 drag factor which is really not best suited for LR type bullets. If you can determine the G7 BC for your bullet your drop card data will be more accurate. There is an article on the in the technical articles section, again, written by Bryan.

    http://www.longrangehunting.com/forums/f5/berger-bullets-move-g7-standard-bc-bryan-litz-44399/

    Velocity is the other variable which can be known with the use of a chronograph, however, not all chrony's are 100% accurate. Some may be up to 5% off. If you have a way of comparing to some other chronies you should be able to gat a good idea of how accurate it is.

    When shooting at various ranges you want to record all the enviromental data, like pressure, temp and elevation.

    There is more than one way to go about validating your BC and trajectories. The most common is probably by measuring your drops at different ranges. And another is comparing velocites from your muzzle to somewhere down range. You need two chrony's for that.

    I'm sure someone else will chime in with some good techniques.

    -MR
     

  3. Michael Eichele

    Michael Eichele Well-Known Member

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    I am short on time but a few things that come to mind are that 20 MOA tappered bases help. Make DARN sure your scope is level with the receiver, also use an alignment bar kit to ensure your rings are lined up properly. Lap them need be.

    After load development, I sight her in perfectly at 100 yards AND 300 yards. Then I shoot over two chronies to get me a BC. 3 different times this year I have made a 1st round hit in the X ring at 650 and 700 yards using this method. 1st round meening I had never fired that load farther than 300 yards previously. Once you have this info, I prefer to shoot at 300, 450, 600, 700, 800, 900, 1000 yards to get a more precise drag model and BC. You must absolutely make sure you posotively KNOW the temprature, barometric pressure and humidity to calculate a precise drag model and BC reguardless of what method you use. The BC of any bullet will change with velocity so test it for sure.

    Dont pull your hair out if your long range impacts are to the right of center a bit. This is normal. Learn how much and compensate for it. Spin drift and coriolus are not ficticious.

    As a side note, I have used some bullets that in theory should have worked best with a G7 model and in fact worked best with either G5 or even G1. It is what it is. Do your own tests and compensate accordingly.

    Get some ballistic software and learn how to use it to your advantage.

    PRACTICE PRACTICE PRACTICE!!!!

    Have fun.
     
    Last edited: Jul 16, 2009
  4. bcoving

    bcoving Well-Known Member

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    Jun 14, 2009
    Thanks for the input. I guess I just got to get out there and start shooting.