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Reloading Berger Bullets

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Temp sensitivity

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  #1  
Unread 04-19-2013, 04:27 PM
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Join Date: Dec 2011
Location: Easterm Idaho
Posts: 42
Temp sensitivity

My question is how do you find the temp sensitivity of your gun powder. I am guessing Ave on a chrony. I would think though this info would be published but I can't seem to find it. Right now the powder I am working on is h4831sc. Thanks for the help
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  •   #2  
    Unread 04-19-2013, 04:55 PM
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    Join Date: Dec 2011
    Location: Michigan
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    Re: Temp sensitivity

    You can do it on a chrony, or by looking at poi changes and backing that into velocity. H4831sc is an extreme powder and should be relatively stable.
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      #3  
    Unread 04-20-2013, 01:17 AM
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    Join Date: Sep 2005
    Location: Central AZ
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    Re: Temp sensitivity

    Even with temp sensitive powder, you will have some big changes in POI with 20 degree change in temp. Every little thing counts in extreme LR shooting. If you are serious about finding out, get an infrared thermometer from Harbor Freight for $21. Put your cartridges in the freezer the night before. Transport them to the range in a cooler, then pull them out and shoot them over a chrony every 20 degrees of increase - say 30, 50, 70 and 90 degrees (for us AZ rats). You may be surprised at what you find.
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      #4  
    Unread 04-20-2013, 03:39 AM
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    Re: Temp sensitivity

    How does one measure the temperature of powder inside the case with an IR thermometer?

    Pointing mine at a cartridge only measures the temperature of the brass case. Cartridge brass does not have the same temperature rise coefficient as smokless powder. The heat transfer coefficient of brass is 315; copper jacket's 389. For cellulose (closest thing to smokeless powder I could find) is .039. So the case will heat up much faster than the powder.

    I have observed that the longer a cartridge stays in a hot chamber, the faster the bullets leave. With a .308 Win. cartrodge, every 30 seconds of chamber time requires a 1/4 MOA reduction of sight elevation for 1000 yard targets. 30 caliber magnums need a 1/4 MOA change down after about 20 seconds.
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      #5  
    Unread 04-20-2013, 04:08 AM
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    Join Date: Aug 2003
    Location: NC, oceanfront
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    Re: Temp sensitivity

    Quote:
    Originally Posted by Thumper1991 View Post
    I would think though this info would be published but I can't seem to find it.
    There is no published data to even try & apply for this. Also, you should not allow marketing hype to lead into assumptions.

    It's just an area that has to be tested in your gun, with your lot# of powder & load, at different conditions. If you plan to use the same barrel for a wide spread of conditions, then you can keep a log and expect compromise across some of the range.
    I have summer guns that never leave the safe until temps get above 85degs. They're used only for hunting at high temps, where my hunting loads were developed, so I don't burn up any barrels shooting at lower temps -in an effort to produce some sort of universal guns.
    I also keep ammo in my pants pockets, while load developing, and while hunting, single loading rounds just prior to actual shots. I do this hot or cold for any hunting gun. I also keep a hunting barrel acclimated to the field temps, by keeping them in shaded cases outside during hunts. They can take a couple hours to stabilize otherwise.
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      #6  
    Unread 04-20-2013, 05:01 AM
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    Join Date: Dec 2001
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    Re: Temp sensitivity

    Quote:
    Originally Posted by Thumper1991 View Post
    My question is how do you find the temp sensitivity of your gun powder. I am guessing Ave on a chrony. I would think though this info would be published but I can't seem to find it. Right now the powder I am working on is h4831sc. Thanks for the help
    I read some of your prior post seem like your pretty good hunter on deer/elk plus loading for a friend and he did pretty good with your loads using H-4831sc.

    Since you live in Idaho maybe you could find place close to where you hunt check you POI at varies yardage. I use H-4831sc in my 30-338mag and I've had that rifle out to maybe 20 below on elk here Co never had a problem with it. I know Hodgdon put something out on their powder not sure it comes into play in the real world of hunting.

    Well good luck
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      #7  
    Unread 04-20-2013, 05:55 AM
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    Join Date: Dec 2008
    Location: Great Falls, MT
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    Re: Temp sensitivity

    I too use the H4831SC (6.5x55, .270AI, .300 WM, .338WM) with very good success hunting in Montana's adverse weather conditions.



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