C ROY,
Big Game has been the most temp-stable in my tests across a variety of cartridges, but Magnum has been pretty good as well in a smaller range of rounds--but it's more of a specialty powder than Big Game. Hunter tends to lose around 100 fps from 70 to zero in most rounds, but whether that makes any difference in POI depends on the rifle. TAC is VERY temp-stable in the rounds it was designed for, the .223/5.56 and .308/7.62, but not so much in cartridges outside that basic powder capacity/caliber ratio.
