BC Variance... and effect at 1000 yards

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by yote bomber, Sep 19, 2008.

  1. yote bomber

    yote bomber Well-Known Member

    Mar 3, 2008
    I ran across this article the other day... pretty interesting, so I thought I'd share it. I've noticed that I tend to string shots vertically at 800-1200 yards with the Berger 210s out of my .300 RUM... couldn't figure out why... maybe this is the answer.

    Whidden Bullet Pointing Die System

    For those of you who don't want to sort through the article... it states that the average variance in BC in a single box of MATCH bullets is .019... with plastic tipped bullets being the most consistent. Who knows what the variance is in a box of hunting bullets...?

    Here's a quote from the article:

    At 1000 yards ….

    1. An Extreme Spread of 0.010 in BC values in a group yields about 3.75" of vertical. Take note--that is the kind of BC consistency a serious 1000-yard shooter needs.
    2. An Extreme Spread of 0.020 in BC values yields about 6.75" of vertical. (Remember the AVERAGE BC spread found in bullet samples was 0.019, so this is typical.)
    3. An Extreme Spread of 0.040 in BC values generates nearly 12.5" of vertical. That's more than a full Minute of Angle!

    I know many of us strive for those low SDs on loads to eliminate vertical strining at extended range... but if your BC isn't consistent... you're shooting yourself in the foot.

    Just a little food for thought... I know I'll be doing a little more work with the 208 A-Max after reading this article.