Exbal Question ?? Trajectory Validation

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Down Under Hunter, Jun 8, 2008.

  1. Down Under Hunter

    Down Under Hunter Well-Known Member

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    Went out the other day and re zeroed and tested my 338 out to a range of 940M.

    I chronoed the rifle at 2852 av for the 300 smk.

    I shot the targets based on this velocity figure in exbal and was fairly satisfied that we were dead on.

    Went out 2 days a go for some more shooting. Lined up the 695 M target and entered the new conditions. Got the new dope ( Shot the target with the same ups 15.75 as shoot one. Got a group that was 9" low ?

    So went back and re validated and got a corrected velocity figure of 2819 fps. This was because I needed to come up around .5 moa. 16.25 moa put me close.

    I just wanted to know if you go out and practise, is it normal to have a trajectory validation changes from session to session ?

    From what I saw Shawn Carlock talking about on his LRH DVD, you will find an average velocity based on multiple sessions of testing ? Some days the gun is looking quicker or slower. Then take the average to run with ?? Does this sound right ?

    I checked all my rig and it was all square.

    Just wondered if any of you experience this and if it is normal for exbal ?

    The only real diffence in conditions was the RH had gone from 93 % in shoot one, to 79.4% in the second. BP was 29.72 To 29.88.

    Thanks again all !!
     
  2. Mikecr

    Mikecr Well-Known Member

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    Would need details to figure it out.
    What were the temps and altitude?
    Was the 29.72" raw, station pressure?
    What was your BC entered?
    With the 940m chronograph testing, what was your ES?
    Did you re-chrono to get the corrected velocity value of 2819?
    Do you think the ammo was the same temp?
    Was the gun fouled the same?
    Was there a cleaning in between 940m, 695m?

    An average velocity will only work for you if the results still fall within the killzone of your target. This is a imiting factor as far as effective range of your 'system'. Do you feel like you can pull up and with a single shot, and hit your killzone at 940m?
    Be honest now. There is no 'average' to it, nor walking shots into a barn door. What size is your killzone?
     

  3. Down Under Hunter

    Down Under Hunter Well-Known Member

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    I roughly have a 24 " killzone.

    I aim at a 4" round circle and found the group 9 " low.

    I use raw stn pressure.

    First time the group was shot from a fouled barrel. The next it was shot clean.

    I basically just want to know if guys revalidate data more than once with the exbal program from session to session.

    Cheers

    DUH
     
  4. Mikecr

    Mikecr Well-Known Member

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    All I can say(without the data) is that it's not an Exbal problem. It's your load and/or barrel.
    Unless competing, your impacts should always make sense. That is, once you've worked out the bugs.
     
  5. jwp475

    jwp475 Well-Known Member

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    Clean barrel VS fouled barrel velocity what is the difference in your barrel? Also was the lighting the same both times you shot at your target?