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Hi all. My IDPA load is a 200g LSWC over 5.5g of 231 with W large pistol primers. Out of my Baer PremierII, this gives me a velocity of 870 and a power factor of 174 (IDPA power factor for .45's is 165).

The couple of times I have chronoed this load it has been during a hot summer day with temps between 75-85 degrees. What will happen to the velocity of this load when I start shooting it in 50 degree weather? Will it go up or down, and why? Any estimates on how much of a move up or down for 50 degree weather? Thanks in advance.


Regards,
Frank
 

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It will decrease...

...I don't know by what amount for your gun and load. I do know the army did tests years ago with the 7.62 and that the overall outcome was that there was a measurable difference for each 10 degrees of temperature. It would certainly be worth knowing if you are cuttin' it close.
I'll look for the data and post it when I find it. As I said, the reports I read were on the 7.62. I don't remember which load.
 

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Don't know about W231 but I understand some powders can be more temperature sensitive than others. I personally left some .45 loads with WST in them in the car overnight recently. Temperature got down to 55 degrees. Went to shoot them in the morning when it was still only 63 outside and found some of them wouldn't quite cycle the slide. These normally run fine in 70 plus degree weather. They're also at the low end of the power scale.
 

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I have found that the Vhit powders are not at all temp sensitive. I chronoed rounds I had froze the night before then got them to the range in a cooler. Put 10 more on the dash for 30 minutes. No difference.

Most Winchester powders will loose vel when it’s cold. Some can actually gain. I can’t remember what powder it was, but I was blowing primers at an alarming rate in my 40 a few years back.

AA2015 in my 22BR doesn’t like it when it’s hot. Too bad as it’s a great prairie dog load. I had to switch to Varget as it usually gets over 100 up in Wyoming and SD where I hunt.

Tom
AF Shooting Team
 

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As I understand it, the velocity decreases because the pressure decreases in colder weather. The point...? Only that if you developed a load that was pushing the edge in winter-time, it might be over it in summer, so make sure to double check things.
 
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