Ballistic Calculators???

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by shortpants, Jan 26, 2011.

  1. shortpants

    shortpants Well-Known Member

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    I am trying to find 3 or 4 of the best factory loaded ammo for my 300wsm. as I am not set up to reload at this time. I have been using ballistic calculators to help narrow my search. I have been using 165gr. Fusions for the past 3 seasons with good success. My ballistic data was obtained without using tables or calculators but by shooting only and it has proven time and again to be very accurate in both drop and drift. The problem is when I take my proven data and plug it into a calculator everything is way off. Fusion says that bullet has a b.c. of .453 but for me to be able to match the calculated drop to my actual drop I have to drop the b.c. to around .320 and I can't get the drift to match no matter what I do. I have tried for many hours and made sure all the data I am entering into the calculators is accurate including the enviornmental parameters. If I can't take known data and make it work on a calculator how can I trust the given data when shopping for new ammo? It would take me years to buy,shoot, and compare all the different choices out there. I believe the problem to be my lack of experience with calculators because those of you who know how to use them swear by them. If someone can help shed some light this way cuz I'm having trouble seeing!
     
  2. J E Custom

    J E Custom Well-Known Member

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    That is a problem that everyone faces if they use the factory BCs.

    Those BCs are always Best case scenario and are based on the GI profile because the numbers
    are much higher and sell more bullets.

    In reality the G7 Profile is closer to the actual performance of the modern bullets but will have
    a much lower number.

    To me the number does not matter as long as it is accurate from the performance stand point.

    The best way is to verify the actual drop with a 100yard zero at 300 and 600 yards and change
    the BC number in the computer until it closely matches the actual performance of the bullet/load
    combination and use that Number for that bullet/load on all distances and you will be close.

    J E CUSTOM
     

  3. bigngreen

    bigngreen Well-Known Member

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    The first question that came to my mind was how are you getting your velocity data? Published specs are likely to be of so if your not using a crony to get an accurate velocity then I would tweak velocity before BC and see how that goes.
     
  4. Michael Eichele

    Michael Eichele Well-Known Member

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    Welcome to LRH.com From CWT.com

    I'll call ya around 14:00 your time.

    M
     
    Last edited: Jan 26, 2011
  5. JUDD

    JUDD Well-Known Member

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    That's what I was thinkin also
     
  6. shortpants

    shortpants Well-Known Member

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    The answer is I have never shot it through a chrony because when you develope your drop chart by just shooting various ranges without adjusting the turret from 100yd. zero and then measure the drop it does not matter how fast your bullet is traveling. It is a long process however, and that is why I don't want to go through it for every bullet choice available, that would take years. I have tried adjusting the velocity in the calculator without adjusting the b.c., adjusting the b.c. without doing the velocity, and tried adjusting both. The question is how do you compare bullets in a calculator when you don't have a true velocity or b.c. since all the manufacturers are inflating their data? Even if I knew my velocity it would not match what the calculator is saying?
     
  7. JUDD

    JUDD Well-Known Member

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    We shoot the rifle through a Chrono and that takes one variable out of question. Then shoot at various ranges to compare the drop chart with the advertised BC. Adjusting the BC to and Fro to get the curve that best matches our chart.
     
  8. shortpants

    shortpants Well-Known Member

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    That makes perfect sense I'm just trying to avoid buying 10 different boxes of shells to narrow down to 1 but that would obviously be the most accurate way. I would like to find one and stick with it and even have a custom turret made. I can shoot to 500yds. with confidence right now with the 165gr. Fusions but they seem to fall apart after that. I think I can extend my range a little more by experimenting with some 180gr. bullets. I do shoot quite a bit up to 800yds. and have got a 7''group at 800yds. with those 165's but I'm only interested in first shot on target accuracy (groups mean very little). Whenever I can afford to move I will get into reloading but where I'm at now it is not possible with my little ones around.
     
  9. J E Custom

    J E Custom Well-Known Member

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    Good question .

    Sorry I did not elaborate,(Normally I do) I use a chronograph for all testing, and assume
    that any serious shooter that can afford one does the same.

    And armed with the velocity and the trajectory they will give you an accurate BC and the performance range of the bullet. But be sure and use the G7 BC with your computer
    for best results.

    I never believe published data because it rarely matches your performance because of
    barrel difference and climate.

    I live 18 Feet above sea level and every test is slow and low compared to the altitude
    and humidity of the published data location.(Normally 5000 to 8000 feet with a 30%
    humidity) Our humidity is normally 95% and up.

    J E CUSTOM