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Temperature Sensitive Powder

Discussion in 'Ammunition & Reloading' started by sleepygreen, Dec 2, 2014.

  1. sleepygreen

    sleepygreen Moses Lake Member

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    I am new to reloading but have found everything I need to reload .223. Of course my main priority is to be safe. The powder I have is winchester 748 and I have read that it can be temperature sensitive. It is very cold right now where I am, and I will probably shoot a lot in summer when it is very hot. Temp difference of upwards of 90 degrees. Other than loading and testing closer to when I will be shooting, what recommendations do you have for a safe, year round plinking round? I understand that I will sacrifice some accuracy. I will be using:

    Mixed head stamp brass
    Cci 41 primers
    W748 powder
    Hornady 55gr fmjbt


    Also, is there a problem loading 5.56 cases to .223 specs?
     
  2. Trailboss

    Trailboss Vancouver, WA Well-Known Member

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    For me, Varget has been very consistent at all temps I shoot at (hot summer to -10).
     
  3. Joe13

    Joe13 NW of Vancouver Opinionated & Blunt Bronze Supporter 2015 Volunteer 2016 Volunteer

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    5.56 is a higher pressure round then .223, you should be fine.
     
  4. AMProducts

    AMProducts Maple Valley, WA Jerk, Ammo Manufacturer Silver Supporter

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    Varget, and other IMR type single base powders tend to be less sensitive to temp. Varget is notably so.

    For .223/5.56, my personal fav is SMP735, which is the canister version of H335. I load 25gr and go, depending on what loading manual you use, this is anywhere from about .3 to 1gr less than MAX. I have shot this load everywhere from hunting out around yreka last year (it was too cold for animals to come out at -2F so we did some target shooting), to shooting in the desert over the summer at 120F out near the salton sea.

    I think the bigger issue you're going to have, is having a loaded round in a hot chamber, where the temp swing can be from -2F all the way up through 300F if you're really letting loose.
     
  5. jluck

    jluck Really,Really, Close to Newport Oregon 97365 Voted #1 Member

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    Is there any definitive guide for powder temp stability? I see lots of opinion and "personal" experience but never any real evidence or published data.

    I have high hopes for Varget myself as most of the time I see people say it IS temp stable.

    I have had good luck (with my hunting/shooting need) with Reloder22 but some say its super temp sensitive. I would like too see some sort of (reliable) published data like a burn rate chart for temp stability.
     
  6. AMProducts

    AMProducts Maple Valley, WA Jerk, Ammo Manufacturer Silver Supporter

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    I think the question is more what are your criteria for what is temp stability.

    While in general, I find that varget has very even performance across a wide variety of temperature conditions (environmental) IMR3031 tends towards more even performance in my .308 loads. Thus going from cold weather conditions where I may get 2500FPS out of the load, and I may be getting 2650 on a hot day, I have never been in a place where temps went from 30F in the morning to 90 in the afternoon. So the temperature stability for match ammo is much less important. On the other hand, varget has long been my choice for loading hunting ammunition as I don't need the same consistency, but I do need the higher performance.