Actual vs. published bc

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by swizzler, May 17, 2013.

  1. swizzler

    swizzler New Member

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    What is the best/easiest way to determine actual bc of a given bullet without being an engineer or mathematician?
     

  2. Rbreb13

    Rbreb13 Member

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    Most of the time I just use what the mfr. publishes. Usually they're close enough.
    If you want to get more in depth, this site can help.
    all about bullets
     

  3. Mikecr

    Mikecr Well-Known Member

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    That's an article about greenhill TWIST calcs, and not BC..
    There is no 'easy' way to determine -actual- BC. Your best bet is to use BC data from Bryan Litz's book: AB for Long Range Shooting
    And learn to use the latest in ballistic software in conjunction.
     
  4. varmintH8R

    varmintH8R Well-Known Member

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    What software do you run?
     
  5. JeffVN

    JeffVN Well-Known Member

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    most of the recently published BCs are fairly accurate; prior to the last few years the Bcs on lots of bullets were heavily inflated. Sierra being the only real exception - since they have always released banded BC tired to velocity. Many ballistic software manfacturers had now fully integrated the newer bc numbers.

    I know the Bcs in my android app (shooter) are pretty good, out to about 1,500 yards. After that, they numbers are still too high and you need to do your own banded velocity inputs. My brother uses Field Firing Solutions, and its pretty good out to a mile (1,760) and it lets you modify the inputs to reflect actual results.

    The site JBM Ballastics has a good calulator that includes pretty good bc.

    Jeffvn
     
  6. MontanaRifleman

    MontanaRifleman Well-Known Member

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    I think you will find Bryan Litz' BC's to be very accurate. I use his. But if he hasn't calculated one for a particular bullet, I use the manufacturer's BC as a starting place. Then I shoot the bullets and confirm drops at different ranges. Then I fudge the velocity and BC to get the closest curve for my load and rifle. To do this right, your info must accurate. Scope height, accurate zero, accurate groups and interpretation, accurate environmental conditions and the farther you test your drops, the better.