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Linearity of powder temp sensitivity

Perhaps I don't have the right search parameters, but is there any information out there on the change of velocity vs temp that gives the change as a graph rather than an average over the temp change? Most temp insensitive powders say they stay within an average of, say, 25 FPS from 0 to 100 degrees. This is an average, even though maybe the velocity with change 20 FPS from 0 to 50 and 5 FPS from 50 to 100. (not actual numbers of course, just a for instance) A powder like this might be better for a target shooter developing loads in 75 degree weather and shooting in the hot summertime, while it might be more critical to a hunter who develops a load in early fall at 45 and hunts in the snow way below freezing. If you understand what I am trying to ask, I would love to hear about your summer vs winter powders. If there are non linear changes like this or if one powder is just tweeked to match the temp across the board. Thanks guys. John

PS: I tend tend to avoid load development in the hot and cold extremes, so critical variations from around 70 up and down for the situation is why I ask.
 
Check this article out, it details some info about temperature stability. In the article the author says:

At the Applied Ballistics Seminar in March, Bryan Litz gave his rule of thumb for how muzzle velocities may vary with temperature for different types of rifle powder:

  • Good Double-Base Powders: 1 fps per degree Fahrenheit
  • Average Single Base Powders: 0.3-0.5 fps per degree Fahrenheit
  • Best Single Base Powders: 0.1-0.2 fps per degree Fahrenheit
 
The burn rate of loose powder may be close to linear over a fairly small temperature range, but the wider the range, the more likely it will not be in loaded rounds. It's not just temperature that affects burn rate, pressure does as well. As the temp goes up and burn rate increases because of it, pressure will increase as well, thereby causing the burn rate to increase even more than it would just from the temperature increase alone.

One approach to solving this issue is to try and set "bookends" for your loads, determining empirically what charge weight is necessary to maintain approximately the same velocity in temperatures at both the low and high end of the range at which you're most likely to shoot. If you know the appropriate charge weight for the lowest and highest temps you're likely to shoot in, it's a little easier to make a good estimate of the appropriate charge weight for temps in between. I try to get good velocity data sometime in early spring/late fall for the low end, and during July/August for the high end. I can then plug those values into QuickLoad and get a decent estimate for any temperature in between. It's a little extra effort, but can pay off in matches if you live in a region with significant temperature swings (i.e. >40-50 degrees F) during the different seasons.
 
Check this article out, it details some info about temperature stability. In the article the author says:
This is the kind of information I see most of the time, an average per degree or the average across a wide temp range. I am wondering if the powders may be either more cold senisitive or heat sensitive; most of your change in the cold range or hot range. For instance an average of 1FPS per degree overall may be 1.5 FPS below 50 degrees, and only .5 FPS above 50, or vice-versa. ALso, there may be a point in the range where 5 or 10 degrees yield the same result.
 
I'd be happy enough if powder makers told us ANYTHING meaningful about their powders..
Like what is '4350' as a standard? What are the tolerances for attributes making up the standard?
Since we don't have this information, and knowing that each powder is actually different from lot to lot, we're left to test what we hold locally (for what matters locally).
 
This is the kind of information I see most of the time, an average per degree or the average across a wide temp range. I am wondering if the powders may be either more cold senisitive or heat sensitive; most of your change in the cold range or hot range. For instance an average of 1FPS per degree overall may be 1.5 FPS below 50 degrees, and only .5 FPS above 50, or vice-versa. ALso, there may be a point in the range where 5 or 10 degrees yield the same result.


You can glean a little of that from the chart in the article. While it is a shame they didn't have more bars, one can see that Varget is less sensitive 25-65F than 65-140F. H4350 around the other way.
 
You can glean a little of that from the chart in the article. While it is a shame they didn't have more bars, one can see that Varget is less sensitive 25-65F than 65-140F. H4350 around the other way.
I did notice that, just wondering the same thing about other powders. I really enjoy the research he does on PRB.
 
Cal writes it up but the testing was done by another. It would make a great chapter in the next edition of the Applied Ballistics' series of books...
 

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