Angle Doping

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by TMR, Mar 7, 2007.

  1. TMR

    TMR Well-Known Member

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    Mar 26, 2006
    Can someone explain why when I take the cosine of an angle and multiply it by the LRF distance, it does not match up with exbal? If I use the same angle, I get two different numbers for scope dialing. I am trying to decide if I need an ACI or if an angle finder and the pda will do it.

    Example:
    35* angle(.819 cosine)
    867 yds
    MOA needed = 9.75

    Exbal
    35* Angle
    867 Yards
    MOA needed = 10.5

    Not a huge difference, approx. 6" at that range. Maybe I should just enter the angle in exbal on the pda and go that route. Any advice???
     
  2. Buffalobob

    Buffalobob Writers Guild

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    Jun 12, 2001
    I expect Xbal does the calculation a little differently than you do it.

    Multiply the cosine times the <u>drop</u> for the actual distance you measured. This will get you closer to the correct answer but still no cigar.

    What the cosine of the angle does is make corrections for the angle of the bullet flight with respect to gravity. Because the bullet path is a curve, the angle is constantly changing and is very complicated to compute precisely. Correcting the drop- not the distance -will get you closer to the actual answer.
     

  3. royinidaho

    royinidaho Writers Guild

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    Darn, I wouldn't have thought that the difference would be that much /ubbthreads/images/graemlins/confused.gif

    Guess I'd better get xbal for the pocket PC. /ubbthreads/images/graemlins/frown.gif

    The records (posts) show that of the two methods you use, xbal is the one to trust.
     
  4. Michael Eichele

    Michael Eichele Well-Known Member

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    Multiplying the cosine with the yardage only gets you close. Using exbal will be dead accurate. There is more to it than simply multiplying the two numbers for exact results.
     
  5. Buffalobob

    Buffalobob Writers Guild

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    TMR

    Here are the instructions for the Cosine Angle Indicator.

    Of importance to your question are the last three paragraphs.

    You used Method #1 and Method #3. I recommended you use Method #2 as being better than #1 but not as good as #3.

    Would you like me to say that one more time real slow. /ubbthreads/images/graemlins/grin.gif



    Drops
     
  6. TMR

    TMR Well-Known Member

    Messages:
    555
    Joined:
    Mar 26, 2006
    BB,

    got it......I will use my PDA and Exbal....unless the battery dies. Then I will get the calculator out.