How accurate are the online ballistics calculators???

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by BENNYBOOBOO, Sep 25, 2008.

  1. BENNYBOOBOO

    BENNYBOOBOO Well-Known Member

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    Have a pretty sweet load for my Savage 10FP in .308 Win that shoots really nice and tight. Unfortunately locally, I only have access to a 200 yard range. But using a JBM ballistics calculator if I enter my actual 100-yard group height(2.5" high), and adjust the speed so that the drop to 200-yards matches my actual 200-yard target (1.25" high). I can then produce a data chart with all the bells and whistles I will ever need.

    If I were to take a drop chart from one of the online ballistics calculators to a 600-yard shooting range, would the numbers produced be close enough to get me on target at the extended ranges so that I can work up an actual tested drop chart?

    EH
     
  2. Varminator 911

    Varminator 911 Well-Known Member

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    I would think that JBM would be plenty accurate enough to get you on target at 600 yds. The errors are more likely to be in things like scope height above bore and actual bc compared to inputted bc, than in JBM errors. But if I understand you right, you are not using bc, rather you are using 100 and 200 yd drops. Using those drops, scope height would be inportant. Also, there would be some error in the drops you are using. Still, I'd think you'd be at least on a 600 yd target, unless it's a really small target.
     

  3. Willys46

    Willys46 Well-Known Member

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    They are accurate, but junk in is juk out.

    If you are confident in you data that you put in I would say it would not be off by any more than 1 moa.

    I used JBM to make a drop chart for my 308. I had zeros at 100 and 300, used there 308 175 SMK and prodcued a drop chart good enough to win a sniper match. longest shot was a 8" steel at 500 yards.

    If getting close is all you need go for it. If going after live animals Double check and verify.

    Willys
     
  4. BENNYBOOBOO

    BENNYBOOBOO Well-Known Member

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    Thanks for the replys. About what I figured. I'm just not interested in letting unnecessary ammo go down range if I can spend five minutes on the internet and save several rounds just to get on paper at (what I consider) extended ranges.
     
  5. Marine sniper

    Marine sniper Well-Known Member

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    For my combo: 300 WBY, 210 Bergers, 2980 fps, JBM is EXTREMELY accurate out to the 900 yards I tested it. The center of the groups were within 1/4 minute (elavation) for 500-900. It was downright amazing.
     
  6. Ridgerunner665

    Ridgerunner665 Well-Known Member

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    I have also had good results from JBM...as was already said, you put junk in, you get junk out.
     
  7. WildcatB

    WildcatB Well-Known Member

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    For JBM to work its best, you need an accurate muzzle velocity. Get a chronograph. An accurate Ballistic Coeficient is also necessary. I've had good luck with published BC's, but you can use JBM's Ballistic Coeficient calculator to get a more accurate one. You'd need a chrono for this too.
     
  8. britz

    britz Well-Known Member

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    I have also had great luck w/ JBM. Testing my 300 to 900 yards and good results. I had to do some playing around with the elevation above sea level inorder to get good results, but after some playing around with a 200 yard zero and testing at 500 to measure the drop, I am very pleased with my current drop charts made by jbm.