I’d research some of the hogdon extreme line of powders excellent temp stability. I’ve personally used hogdon varget in .308 with excellent accuracy and hogdon h1000 in my 7mm before making the switch to vit N570 for more velocity but both trials of hogdon produced great accuracy
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Or check out midsouth shooters supply, brownells, midway USA, Graf and sons , etc many online retailers that have huge amounts of powders.