Calculation of B.C.

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by sscoyote, Jul 17, 2003.

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  1. sscoyote

    sscoyote Well-Known Member

    Feb 26, 2003
    I've seen numerous posts here about the B.C. being calculated/verified by shooting. How is this done? I'm assuming it has something to do with m.v./downrange bullet impact relative to line of sight. Right??
  2. Darryl Cassel

    Darryl Cassel Well-Known Member

    May 7, 2001

    It's actual fire at known ranges to get the clicks or MOA needed to put the bullet that is being used as the test bullet, on target.

    We check the computer drop charts as to what it calls for, using "THAT" bullet to see where this actual fire falls in place.

    If a certain manufacurer says a bullet has a BC of whatever, and you run the ballistics and find that it will need say 20 MOA to get to 1000 yards and the bullet gets there from a 100 yard zero with "less" MOA, then the BC is probably better then listed.
    The reverse is true also if it takes more MOA to get to the same range.

  3. Oli

    Oli Member

    May 7, 2003
    You use two chronographs some distance apart from each other and compare the difference in velocity. I dont know of any english versions so try this swedish one:

    velocity at first chrono (m/s)
    velocity at second chrono (m/s)
    bullet weight (g)
    Altitude (m above sea level)
    Temp. (C)
    Distance between chronographs (m)

    Press "räkna"
    BC appears in red

    [ 07-17-2003: Message edited by: Oli ]