Help Was I thinking correctly?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by kweidner, Sep 12, 2011.

  1. kweidner

    kweidner Well-Known Member

    Oct 24, 2005
    I was working up a drop chart for a 22-250

    Here is the Data

    MV 3695
    Zero is 100 yds
    Sight Height 1.8
    52 Grain Custom Bullet
    .225 bc at a G1 (Educated guess)

    Temp was 80.6
    Pressure was 29.92
    Angle 2.1 degrees
    Altitude 210 feet

    I was shooting at 600 yards. Came up 90 clicks (1/8) MOA to give 70 and change inches of up. The shot was 10 inches low but in a nice little group on my steel. Adjusted my bc value to .200 and it now shows a drop of 80.6 inches given the same variables. I was not able to verify as I ran out of time. Is this what you would have done in this situation?

    I figured my speed was a given , BC was the only thing not certain. I am sure I could repeat and verify but I want to be REALLY close and take out the "Experiment" if you know what I mean.

    I have heard of guys adjusting speed and not BC to get their charts to line up? What do you do? I was taught to adjust BC.
  2. rscott5028

    rscott5028 Well-Known Member

    Apr 18, 2010
    Considering that BC was just a SWAG to begin with, then I'd say it's fine to adjust it.

    Shooting varying distances/conditions with accurate inputs, should help confirm your estimated BC.

    -- richard
  3. Tikkamike

    Tikkamike Well-Known Member

    Dec 26, 2009
    I agree. Some times when trying to find a really close bc I will take an 8 foot piece of ply wood at 200 shoot a group on a spot on top then back up to 400 shoot a group then back up to 600 shoot another without ever adjusting my sights. this allows me to measure my actuall drops, and change numbers on my program till i match my actual results that gets me really close. it also gives me a visual on spin drift reminds me that it is there and i can verify what it actually is also.
  4. bigfellascott

    bigfellascott Active Member

    Feb 23, 2011
    Yep that what I do to TM.

    Shoot at different ranges without adjusting POA to allow for drop, I too want to see where the bullets are landing and then take some messurements and work out how many clicks that relates to on my scope, write it down and just stick it to the cheekpiece of the stock, that way I've got a reference as to how many clicks at that range do I need. Simple but effective enough for me.