Lowering Extreme Spread

Discussion in 'Reloading' started by Firecat, Sep 8, 2011.

  1. Firecat

    Firecat Well-Known Member

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    I have read some post here in the past where some of you have achieved incredible ES numbers from your reloads. Some even in the lower single digits. How did you go about lowering your ES until it was even in the high single digits to low double digits? I have a tight group load for my 7mm that has an ES of 26 Fps. I know that at longer ranges it will begin to open up my group. Whereas if I could get that ES lower it would be more consistent at longer ranges.
     
  2. Broz

    Broz Well-Known Member

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    One thing I learned long ago is to move the chronograph at least 18 feet out when testing. This lowered my ES by at least 20 to 30 fps. Seems the muzzle blast will really rattle the screens.

    Jeff
     

  3. J E Custom

    J E Custom Well-Known Member

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    I work on SDs first and groups later because the SDs are related to powder,primer,case
    size and uniformity,bullet weight.

    If you get good SDs with this combination then try other type bullets of the same weight
    to find out what bullet your barrel likes, and for better groups. then play with bullet seating
    depths for the final accuracy potential.

    Only change one component at a time or you may miss a great load.

    I am allways happy if I get the SDs below 15 on lighter calibers (17 to 6mm)

    With the 7mms through the 338s I look for 10 or lower.

    Oddly enough the big bores are notorious for SDs below 5 (Because the bullet weight
    is normally 350 + grains they are not effected as much by slight differences in combustion
    pressures as are the lighter bullets.

    In general the lighter the bullet the higher the SDs (Of course there are exceptions in some).


    J E CUSTOM
     
  4. JeffVN

    JeffVN Well-Known Member

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    +1 change one component at a time.

    I have been sucessful at reducing my ES and SD by beam-scale weighing every load, playing with primers, and making sure my seating depth is a uniform as possbile.

    I also found that my number became more consistent by annealing my brass, and on some that was uneven in neck thickness, cleaning the necks (meaning turning it to get a uniform thickness). some is very uniform to begin with; some is not, it just depends on the lot. My 7WSM Winchester brass was incredibly uniform over the 25 pieces that I checked with a tube micrometer (in at leasst 4 or 5 spots around the neck) at random from several bags.

    Jeffvn
     
  5. CRNA

    CRNA Well-Known Member

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    I am interested in some of the responses to this question as well. I usually put my chrono from 10-15 feet from the muzzle. I can't seem to get my ES down no matter what I am trying. Maybe I need to back my chrono up even more with my 7mm.
     
  6. Firecat

    Firecat Well-Known Member

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    I usually try to place my Chrono 6 solid paces away from the end of my muzzle. I know that it has to be between 18 and 20 feet.
     
  7. 80Maro

    80Maro Well-Known Member

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    I'm shooting .338 LM. I have my chrono about 10ft from the muzzle. Just to give you an idea, my ES on the Barnes 265LRX's over 5 groups were 36, 66, 71, 127, 173. On the 300gn SMK's it was 11, 17, 18 and 27 over 4 groups. You can see the difference. Also, the 300gn SMK's shoot very well versus the 265LRX's.
     
  8. woods

    woods Well-Known Member

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    This thread got me to thinking so I went back through my spreadsheets to find some low ES shot strings. Ran across this seating depth test and decided to run some numbers on ES and SD to see if there was an correlation and input the data onto the target to get a clearer picture

    [​IMG]

    These loads were all outside neck turned, neck sized with Lee Collet for .003" bullet grip, new cases, dry lubed with mica, seated with comp seater/comparator, loaded at the same time and shot at the same time.

    From the data and target it looks like the seating depth of .060" off OR A VELOCITY around 3175 fps would be a node of accuracy and stability. Unfortunately I picked the 3200 fps load and have a bunch loaded because I had not paid attention to ES or SD

    Time to do more testing