What is going on here?

Discussion in 'Long Range Hunting & Shooting' started by carpetman2, Sep 28, 2013.

  1. carpetman2

    carpetman2 Well-Known Member

    Messages:
    250
    Joined:
    Jul 10, 2009
    When I chrono my 300 WM load with the Berger 210 VLD's it averages around 2920 fps. I set the chrono 15 feet from the muzzle. But when I go to the G7 Ballistics Calculator and confirm trajectory at 400 yards it wants to either change the published BC or speed up the bullet to 2985 fps. Which should I trust, my chronograph , the published BC from Berger, or the G7 Ballistics Calculator?
     
  2. MudRunner2005

    MudRunner2005 Well-Known Member

    Messages:
    10,087
    Joined:
    Oct 13, 2008
    I would trust what your chrono says as long as you're positive your chrono isn't reading muzzle blast.

    Other than that, one of the other guys will have to help, as I don't use the G7 ballistics calculator.
     

  3. Broz

    Broz Well-Known Member

    Messages:
    8,637
    Joined:
    Feb 3, 2007
    I have used many 300 wins with 210 Bergers. A max load of H-1000 will get me just over 2900 from a 28" barrel. Using the Shooter app and the factory BC of .631 it worked out with drops to well past 1000 yards.

    Hope this helps.

    Jeff
     
  4. No Fear in Accuracy

    No Fear in Accuracy Well-Known Member

    Messages:
    318
    Joined:
    Nov 15, 2001
    If you put all data into the G7 calculator, it should give you more accurate information.

    Something like, attitude, air pressure, humidity, etc...
    The chrono will give you the quick answer when you shot on that day.
     
  5. royinidaho

    royinidaho Writers Guild

    Messages:
    8,853
    Joined:
    Jan 20, 2004
    yur never supposed to say "never".

    But, I say, never, never, never, trust the chrono (unless maybe ya paid big bucks for it) UNTIL drop confirms velocity.

    The chrono that is usually used will get you in the ball park. Drop validation will get you spot on.


    I'd use Jeff's bc value then validate.
     
  6. Scot E

    Scot E Well-Known Member

    Messages:
    1,312
    Joined:
    Mar 1, 2008
    Agreed. It is always about trajectory validation. You do have to do your due diligence in setting up the validation correctly with correct inputs for atmospheric conditions, load data, etc. but once you get that down you almost don't even need a chrono. I have gotten pretty good with just loading for accuracy, guessing on velocity from published load data to get me close, then validating trajectory to determine my drop chart, velocity, and shooter ap inputs.

    HTH,

    Scot E.
     
  7. jimbires

    jimbires Well-Known Member

    Messages:
    923
    Joined:
    Mar 16, 2008
    I'd sure use my actual drops . one other thing you need to check , be sure your scope zero , is dead on zero . if the zero is off a little it throws it all off . Jim
     
  8. kcebcj

    kcebcj Well-Known Member

    Messages:
    1,215
    Joined:
    Jan 28, 2008

    Just want to emphasize what Jim says above. If the zero is off even a half inch especially with a 100 yard zero it really messes up things. It has to be dead nuts!! All I use the chrono velocity for when validating the come ups is to get me somewhere on the paper quickly. I note the errors at the different test yardages and use the info to correct the come ups generated by the orignal velocity output of the chronograph.

    A lot of times the chronograph velocities are really close to the corrected.
     
  9. Broz

    Broz Well-Known Member

    Messages:
    8,637
    Joined:
    Feb 3, 2007
    I am all in for adjusting the velocity. (Trajectory Validation) As long as you know for sure all other data is spot on. And yes especially the zero. What ever you are off on the zero will carry through on out. Off 1 moa (1.047") at 100 will be off 1 moa (10.47") at 1000. One thing I have learned since buying some higher end chronographs is, if you trust them they will encourage you to find the real problem. Changing the muzzle velocity might get you on to a certain distance, but if that was not the real problem it will show up again later down range at longer distances. Many shooters seldom check scope tracking to be true to the .25 moa. And no, not that box test at 100. It will not tell you squat, other than the knobs do work. You may not be able to detect a turret that is tracking 1.05 moa, an error of (.043") instead of 1.0 moa at 100, but trust me you will at 1500 yards where it turns into almost 2 moa or 31.5".

    You might be surprised how many scopes are just a little to either side of a true moa.lightbulb

    I just wanted to point out the velocity could fix it at some distances, but if the true problem is something else it is no more than a band-aid waiting to fall off.

    Jeff
     
  10. carpetman2

    carpetman2 Well-Known Member

    Messages:
    250
    Joined:
    Jul 10, 2009
    Very good info guys. I have checked my zero @ 200 and it is spot on. The 100 yard (Ballistic Calculator) tracks perfect. Sooo, I will trust the velocity change and go shoot at 700 if the wind will ever die down, and the rain stop, and see how it is tracking there. Again, thanks for the encouragement and the info.
     
  11. joseph

    joseph Well-Known Member

    Messages:
    1,238
    Joined:
    Jul 26, 2009
    Make your own drop chart by shooting YOUR own rifle so you know what the arc of your bullets is as they go down range.

    joseph
     
  12. WildRose

    WildRose Well-Known Member

    Messages:
    8,210
    Joined:
    Feb 3, 2011
    Yep, I like to use at least three different ranges, 100, 300, 500 will get it done nicely for you.