Load tune?

Discussion in 'Reloading Forum (All Calibers)' started by JohnD, Jan 23, 2019.

  1. JohnD

    JohnD Silver $$ Contributor

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    Im sure there are numerous variables especially powder but can a 40-50 degree temp difference mess up a load tune?

    Thanks, John.
     
  2. Texas10

    Texas10 Gold $$ Contributor

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    Yes. If you develop a fairly hot load in January when its 30-40* F and then try to shoot that same load in July at 100*F, you're probably going to have problem. There are charts on how temperature affects burn rate for many powders that illustrate this fact, one was posted here a few days ago.

    Some fun reading:https://www.shootingsoftware.com/ftp/Pressure Factors.pdf

    http://www.rifleshootermag.com/editorial/fact-fiction-gunpowder-temperature-sensitivity/83518

    http://forum.accurateshooter.com/threads/where-to-get-variation-of-muzzle-velocity-data.3887286/

    http://appliedballisticsllc.com/Articles/Testing for Temperature Sensitivity - PT1.pdf
     
    Last edited: Jan 23, 2019
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  3. JimSC

    JimSC

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    some interesting articles. Lately I have been shooting in the low 30's F to mid 40's F and noticed my ES and SD's seemed off. Now I know why. I may have to carry my ammo in a cooler with a warm brick for these cold winter matches
     
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  4. grovey

    grovey Silver $$ Contributor

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    Now I don't feel so silly for keeping ice packs in with my ammo at a few HOT matches last yr.
     
  5. BenPerfected

    BenPerfected Gold $$ Contributor

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    .....just leave the ammo in your car or truck with the heater on.
     
  6. JimSC

    JimSC

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    last match started a 8 am and finished at 4 pm, that's a lot of idling. I think I will do the cooler and let the bricks warm up on the floorboard during the drive to the range
     
  7. JohnD

    JohnD Silver $$ Contributor

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    I developed a couple of loads last summer when the temperature was 90* and they were very accurate. Tried the same loads a couple of weeks ago at about 40*+ and they shot poorly. A couple of the groups were vertical and that’s what got me wondering about load tune.

    Thanks again, John.
     
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  8. savagedasher

    savagedasher

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    Isn’t bullet speed. Vertical
     
  9. K22

    K22

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    Especially with ball powder. While I've shot some amazing groups with H335 and H380 in my 223 and 22 250 bolt rifles respectively I moved away from ball powder because I hunt and shoot all years around where the summer temps can range from the 90's to winter temps in the 30's and I found too much temperature affect with these powders.

    However even with "stick" powders some scope adjustment is sometimes necessary due to the higher air density in cold temperature versus warm temperatures but for me it usually only about 1/2" or so.
     
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  10. seymour fish

    seymour fish

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    Thinking generally, a wide node and a very temp-stable powder would be required if the load is to stay in tune across that temp spread. Powders have quirks
     
  11. mike a

    mike a 6BR Rocks Gold $$ Contributor

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    And H414 with blow your ass up. Me likes H4350 and Varget.
     
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