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Thread: Powders and temperature.

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    Default Powders and temperature.

    I am fairly new to reloading, and was wondering how big of a role temperature plays with point of impact? Do the hodgdon extreme powders make any difference? I was thinking that if anyone had to deal with extreme temperature differences it was you guys up there!

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    Quote Originally Posted by WEBBYODER View Post
    I am fairly new to reloading, and was wondering how big of a role temperature plays with point of impact? Do the hodgdon extreme powders make any difference? I was thinking that if anyone had to deal with extreme temperature differences it was you guys up there!
    This is a good question, but it has been generally irrelevant to me. While it does get "cold" here, I don't do much hunting in "cold" weather. Normally my season is over by the end of September and the cold is just beginning. This past year was an exception as a good friend had yet to fill his moose tag and hunted the December season. His shot was about 150 yards and it did not get above 25 below that day. No problem for the 375 H&H, but you have to remember the vitals on a moose is about the size of the door on your oven so a couple inches one way or another doesn't make much difference.

    There are changes in velocity with some powders in cold weather, though the change is not always easy to predict and it is rarely a linear change. However, at the range most game is taken, the difference is not significant. I am more concerned with hunting in hotter temps where ammo can get too hot and the pressures may rise to dangerous levels than I am with the 50-100 fps I might lose in "cold" weather.

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    Loads developed in a cold climate for a hunt in a hot climate will produce higher pressures. Likewise loads that I develop down here in Arizona when it's 110 at the range shoot slower and lower when I show up at my brothers house for a fall hunt in Alaska.

    I carefully chart velocities that my barrel likes with certain combination's for best accuracy. Generally it's less than max load. Last year I learned that my loads are slower at 35 degrees and sea level when compared to 110 degrees and 1750 above sea level. I've found that increasing my sweet load in AZ by.4gr registers about the same over the crony in AK as the lighter load in AZ and accuracy remains constant. Since I don't shoot max loads this is an easy adjustment.

    There is a reasonable article in the link below. It's written in other places that extruded powders offer more stability than spherical powders.

    http://www.shootingsoftware.com/ftp/...%20Factors.pdf

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    Temp also effects air density and at longer range I believe this is more of a factor than the small change in burn rate. Unless you load a 22-250 in to hit "X" point at 300 yards in Arizona’s 110f and then try to make a 300 yard shot on a fox in -30f outside Fairbanks its mostly a non issue I believe. Still something to keep in mind in extremes of temp and altitude at longer ranges though.
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    Check the latest American Rifleman, and an article by John Barsness on this very subject.

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    I haven't seen what Barsness has written about this subject but I'm sure I know as much about it as he (he may disagree). Generally the more modern powders, either in nomenclature or those with old numbers and new manufacture are more temperature stable. The Hodgdon extreme series is very temperature as is the Vihta Vouri powders and some of the new propellants form Alliant (10X). This will give smaller velocity spreads due to temperature swings but these velocity variations cannot be seen as trajectory error in the field.

    In extreme case such as with some ball powder which has high velocity swings, at the longest ranges, and with 100 degrees or more of temperature variation, with an expert shot, one might use this as an excuse for missing a prairie dog. Velocity variations, extreme spread (ES), as its called form any ten shot batch with a large capacity magnum cartridge will typically be about 40 fps. I have seen as much 100 fps ES and more, all at the same temperature. I have also seen 100 fps less mean velocity from 80F degrees to -25F with the same 300 Winchester magnum load/rifle when the 80 degree shoot had an ES of 28 fps. Can you shoot well enough at 300 yards to find impact errors with a 100 fps velocity difference?
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    Quote Originally Posted by Murphy View Post
    I haven't seen what Barsness has written about this subject but I'm sure I know as much about it as he (he may disagree). Generally the more modern powders, either in nomenclature or those with old numbers and new manufacture are more temperature stable. The Hodgdon extreme series is very temperature as is the Vihta Vouri powders and some of the new propellants form Alliant (10X). This will give smaller velocity spreads due to temperature swings but these velocity variations cannot be seen as trajectory error in the field.

    In extreme case such as with some ball powder which has high velocity swings, at the longest ranges, and with 100 degrees or more of temperature variation, with an expert shot, one might use this as an excuse for missing a prairie dog. Velocity variations, extreme spread (ES), as its called form any ten shot batch with a large capacity magnum cartridge will typically be about 40 fps. I have seen as much 100 fps ES and more, all at the same temperature. I have also seen 100 fps less mean velocity from 80F degrees to -25F with the same 300 Winchester magnum load/rifle when the 80 degree shoot had an ES of 28 fps. Can you shoot well enough at 300 yards to find impact errors with a 100 fps velocity difference?
    Don't forget that it goes hand in hand with air density and at longer ranges air density will have much more effect than powder burn I believe. Cold air is thick, hot air is thin, and it takes more energy to move something through thick air.
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    Quote Originally Posted by ADfields View Post
    Don't forget that it goes hand in hand with air density and at longer ranges air density will have much more effect than powder burn I believe. Cold air is thick, hot air is thin, and it takes more energy to move something through thick air.

    I'd say that is true. This velocity variation, temperature, air density altitude and possibly the sign of the moon may matter but none as much as the human behind the trigger and that of course is the weak link in this chain. Don't sweat the small stuff and this is all small stuff. As my old shooting coach used to say to me; shut up and shoot.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Thanks Murphy:

    That's better'n the article,

    which IIRC, doesn't disagree with anything you've said here.

    Smitty of the North
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    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

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