Chronograph ES and SD

Discussion in 'General Discussion' started by mo, Jun 4, 2009.

  1. mo

    mo Well-Known Member

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    I have a chronograph, and it works very well, but the only time I use it is when I'm making a drop chart on exbal. I still do it the old fashion way leg work, and shooting. I pick my best groups, and that's what I go with, and it seems to work fine. I don't care what the ES or SD number is as long as it shoots well!

    Now for the question. Could a person just shoot through a chronograph at no target, pick out the best ES and SD, and that be his load? Does a low ES and SD number mean that it will shoot good? Can a high ES and SD number out shoot a low number? Just curious. Thanks for reading.
     
  2. AJ Peacock

    AJ Peacock Well-Known Member

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    No, low ES and SD don't gaurantee a good long range group. However, I'd bet on a load with a low ES/SD over another load every time.

    No, in my experience, a high ES/SD will give you too much vertical at long range.

    AJ
     

  3. phorwath

    phorwath Well-Known Member

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    What AJ said - presuming you are asking about good loads for use at long range - like 500-600 yards and farther on out. Your post didn't state your intended range of use.

    If your muzzle velocities vary too much, they will cause elongated vertical spread in your long range impacts - best case scenario. Worst case scenario, the loads may just not shoot worth a $hit.
     
  4. J E Custom

    J E Custom Well-Known Member

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    What you are looking for is a SD in the single digit's (ES will improve as SDs go down) "AND"
    good groups.

    At short distances you can have good groups and poor SDs but at long distances the groups
    will fall apart.

    In order to have good groups at long distance you will have to find a load that has=Good
    velocity,good SDs,groups well at 300+yards and a bullet with a high ballistic coefficient.

    When I start working up a load I always start with the chronograph to get the best SDs
    (This tells me that I have a good powder, primer and bullet weight combination. then I experiment with bullet seating depth to improve accuracy.

    J E CUSTOM
     
    Last edited: Jun 5, 2009
  5. mo

    mo Well-Known Member

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    Thanks for your comments. Sounds like you can take some guess work, and a little leg work if you use a chronograph.
     
  6. J E Custom

    J E Custom Well-Known Member

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    Before I started using a chronograph Testing was hit and miss,I had one rifle that I just could
    not make it group (I tried over 70 different loads) .Frustrated I decided to start over and shot
    some of the left over test rounds through the chronograph and tryed to figure out what was
    wrong.

    The third load I shot had a standard deviation of 09 but grouped terrible ( almost 2"). so I went
    to a SMK of approximately the same weight to eliminate the chance that the hunting bullet was
    of poor quality. The SMK shot almost the same so I was back to square one.

    Not knowing what to do next I decided to try different bullet seating depths with the same load.

    I started .050 thousandth off the lands and moved closer in .010 thousandth increments
    watching pressure signs.

    The closer I got the better it shot up to .020 thousandth. .010 did not shoot any better and .005
    gave me signs of pressure.

    Different Bullet designs may dictate seating depth so you just have to experiment once you have
    a good powder,primer,velocity and bullet weight combo (Lo SDs).

    This rifle is a 30/338 and will shoot sub 1/4 MOA groups all day long so using the chronograph
    saved a great rifle that was destined for the donor pool.

    Since switching to this method for working up new loads I have cut my time and cost by 75%
    and with prices now days that's a big plus.

    Don't get me wrong you can still find accurate loads buy trial and error and maybe luck out with
    only 1 or 2 tries but if you use your chronograph you will also build a good data base for trends
    with different loads.

    I use the chronograph to eliminate bad loads that would never shoot well and work on the
    ones that show potential.

    This is just the way I approach load development.

    J E CUSTOM