Have experimented with various powders at different temps and find that while many of the newer powders will chrono the same at 0 as at 70, they always produce higher velicities at warmer temps.
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<br>The latest lots of R15 are very cold-insenistive, about like the Extremes. This was a modification made a couple years ago for military purposes; R15 was chosen as the U.S. military rifle powder by Lake City. It also includes a compound that reduces copper-fouling in the bore. I believe you'll be seeing more of this too. Ramshot's rifle powders also feature this. They were also developed for military use, in Europe.
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<br>All powders vary somewhat in burning rate in different rounds, especially when loaded in cartridges with very different bore/capacity ratios. And they all vary some between lots. Powder people say this is because they simply can't control some factors, especially water vapor in the atmosphere, when making different lots. So in some calibers and lots Varget will be slower than R15, even though 15 is generally slower.
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