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Thread: Temp sensitive powders

  1. #1
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    Default Temp sensitive powders

    Generally speaking, at what temp do the "temp sensitive" powders really start being affected? Specifically W760, H414, BL-C(2), etc...

  2. #2
    Dogs Like Him versifier's Avatar
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    Over 90*F and under 40*F.

    At least that's when I've noticed the most dramatic differences. The only real danger comes when you have worked up a load in cold weather that is at or near MAX and then shoot it in hot weather. You can easily go overpressure with a sensitive powder.

    I do just the opposite and first noticed velocity drop in cold weather back in the early 80's. That only was an issue for me when shooting the .22-250 (IMR 3031) very long distances winter varmint hunting - the bullet drop was more than I expected after working up loads the previous summer and I shot just under a few coyotes at 3-400yds before I figured out what was happening. I just assumed back then that it worked that way with all powders. That was long before the internet and general knowledge of temp sensitivity was unknown to any but serious long range competitors. At ranges under 200yds with a deer rifle I could measure more drop on paper (downward shift of POI) from loads worked up with various IMR powders during summer, but the difference has never been enough that I felt the need to readjust my sights. The dead deer certainly never noticed the difference.

    It would be a real issue for long range target shooting.

    IMR4895 was used in military loads for -06 and .308 from day one and it is a fairly sensitive powder, but I never heard any mention of the fact. It is possible the AMU, Marine rifle team, and snipers knew and compensated for it, but it isn't talked about in any of the manuals I've read.

    It's easy enough to shoot some targets on a hot day and save them to compare with some shot mid winter. I have done it with most of my hunting loads over the years. All powders are affected by large temp changes, some more than others. Of the three you listed, I have only worked much with BL-C(2) but have never shot anything I used it for during the winter.
    "Stand your ground.
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    So, I guess the best answer is to do load work during the winter. As it never gets very hot in the summer up here I should be ok with temps at the up end of the spectrum.

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    runfiverun runfiverun's Avatar
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    with some powders i have been able to almost duplicate my summer load with a hotter primer in the colder temps.
    you need to be wary when getting near the top end as a winter rouund could find it's way into summer shooting.

  5. #5
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    I generally do my load work in the warmer weather, what we have of it up here and do my loading of tests for the next season when the snow is too deep to use the range - December or January until well into April. I like hunting on cold brisk days, but I don't much enjoy freezing off my nether regions sitting in the wind at the range when it's too cold to get the pen to write on the test targets and I am rapidly losing feeling in fingers and face from exposing tender flesh to Frostbite Falls weather.

    Seriously though, a load you work up in the hottest weather will ALWAYS be safe in your rifle at lower temperatures. Your velocity drops (how much depends on the powder and how much the temperature difference is) and your POI at longer ranges drops sooner and faster, but predictably once you have shot the load throughout the year and kept records of either the chrono readings or the amount of POI shift at a specific range as the temps go up and down seasonally. Then you can decide if you want to either vary the load seasonally, or to stick to that load and compensate by aiming higher by a known amount as the temps drop. I used to compensate by aiming higher. It worked pretty well usually. (A mildot scope would have been heaven.) Or you can start all over with another powder known to be less temp sensitive.

    These days the only thing I will be hunting with a rifle in moderately cold weather is deer, it almost never gets below zero in our November deer season, and I know how the hunting loads I use in each of my deer rifles perform down in the twentys, teens, and single digits. That's enough for my present situation. I won't test in colder weather without pressing need for it. I don't know how the deer rifles' loads behave in the middle of February and hope I never have to. But, if you're going to be hunting large game in sub-zero weather, you've got to know how your loads behave and the only way you're going to find out is to shoot in those conditions at the range and keep notes.

    While I did hunt coyotes in the high country in the coldest weather well below zero at higher (Eastern higher) elevations and often in windy conditions, that was when I was in my twenties and thirties. Now I am happily embracing old fartitude and I don't go out when the dog knows better and hangs out by the woodstove. Back then I only needed to test one or two varmint rifle loads for the worst and coldest at their(my) range limits. I knew how those loads behaved when it was really cold. (And it's written down somewhere and maybe has survived family, divorce, the lifespans of three good dogs and a dozen moves around this part of the state. But I did know it then.) If I hunt anything that time of year these days it will be snowshoe hare and only on warm(ish) sunny days with a shotgun that I feed those nice big shells I don't have to take my gloves off to load.
    "Stand your ground.
    Do not fire unless fired upon.
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    - Capt. Parker, Lexington Militia, April 19, 1775

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    My hunting is mostly done between 20-55 degrees...and RARELY do I shoot above 80 degrees. It just doesn't get that hot here, and when it does, I'm not shooting!

    Just read in the new Handloader this evening that BL-C (2) has its performance enhanced in cold weather by using magnum primers. Sounds like a good idea. Will most likely develop hunting loads in colder weather and do similar testing in the summer and compare.

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    How abut puting loaded shells in the freezer??.,OR,in the shade on a hot day??.You can figure out ifin they are safe without the wait,seems like to me anyway.pan.

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    Shooting loads worked up in hot weather during the winter isn't a danger, but doing just the opposite is, though. The problem with cold weather shooting is that there can be velocity loss with certain powders, and just how much varies with the temp and the particular powder. Long range trajectory can be radically altered. Testing your hunting loads in actual conditions over a range of colder temps is the only real way to know how much you're going to lose. Putting just your ammo in the freezer and cramming it into a hot rifle isn't going to tell you anything useful.
    "Stand your ground.
    Do not fire unless fired upon.
    But if they mean to have a war let it begin here."
    - Capt. Parker, Lexington Militia, April 19, 1775

  9. #9
    runfiverun runfiverun's Avatar
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    bet it'll tell you how your rifle will work with a chamber full of condensation.

  10. #10

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    Never had a problem with it down here, and it gets mighty hot here in the summer...
    All of my loading is done in an A/C room that's 71* in the winter and a bit cooler in the summer..
    Tom

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