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Thread: G1/G7 ballistic coefficient diffrences

  1. #1
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    G1/G7 ballistic coefficient diffrences

    Saw this thread, and it was informative..bc changes as a factor of velocity...
    Some projectiles refrence it, others do not..

    It was a decent read on page 2..
    http://thefiringline.com/forums/show...=555006&page=2

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    Graduate Airgator0470's Avatar
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    Quote Originally Posted by mapper View Post
    Saw this thread, and it was informative..bc changes as a factor of velocity...
    Some projectiles refrence it, others do not..

    It was a decent read on page 2..
    http://thefiringline.com/forums/show...=555006&page=2
    Some bullet makers offer BC's based off velocity.
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    Graduate seadog's Avatar
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    Quote Originally Posted by Airgator0470 View Post
    Some bullet makers offer BC's based off velocity.
    Yes, they shoot through two chronographs,one at the muzzle and one downrange.
    Crunch the numbers then spit out an average.

    I've read somewhere that the only true way to get accurate bc numbers is by doppler radar.
    Last edited by seadog; December 27th, 2014 at 06:00 PM.
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    So we need to shoot at the giant golf ball at the airport?




    Oderint dum metuant

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    I believe the army has Doppler at Aberdeen testing grounds.
    "Only the dead have seen the end of war" -Plato

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    So does that TV station just North of I-10 on Thomasville road.
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    Shit Stirrer 0utlaw's Avatar
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    ROADTRIP!!!




    Oderint dum metuant

    "Stay with me; do not fear. For he who seeks your life seeks my life, but with me you shall be safe.” 1 Samuel 22:23


    “This gun is liberty; hold for certain that the day when you no more have it, you will be returned to slavery.” – Toussaint L’Ouverture

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    I have seen diffeent bc' based on velocity, seen where some people take a average of the bc then plug that in the drop charts.
    Seen others only give 1 bc, and use muzzle velocity to run charts with..
    Seen others use g7 data...
    It is still an approximation..

  9. #9
    Graduate seadog's Avatar
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    Quote Originally Posted by mapper View Post
    I have seen diffeent bc' based on velocity, seen where some people take a average of the bc then plug that in the drop charts.
    Seen others only give 1 bc, and use muzzle velocity to run charts with..
    Seen others use g7 data...
    It is still an approximation..
    It really helps if you have the bc to velocity numbers for the bullet you are using.
    Tell me what bullet you want to use and I will see if I have the numbers.
    "Only the dead have seen the end of war" -Plato

  10. #10
    Graduate seadog's Avatar
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    Here is an example.

    Fps BCg1 BCg7
    1500. 0.565. 0.314
    2000. 0.629. 0.317
    2500. 0.651. 0.327
    3000. 0.678. 0.332

    Those numbers are for Hornady .338 250gr BTHP Match.

    And of course you probably already know this but I'll say it anyway.
    G1 looks like a pistol bullet,flat base and rounded ogive.
    G7 has a boat tail and a pointy ogive.
    So G7 data reflects most modern bullet designs.
    Last edited by seadog; December 27th, 2014 at 08:39 PM.

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