I haven't tested H322 or X-Terminator in cold, so I don't know about them.
The Hodgdon Extremes are overall the most consistent powders in cold temps that I've tested, but in my tests TAC and Big Game did just about as well as the Extremes. Hunter (and Ramshot) didn't do quite as well, but were still very good.
That said, according to a very experienced lab technician, temp-stability can change depending on the cartridge and application. He used the word "stressed" when describing what happens to a supposedly temp-stable powder when the powder is used outside it's normal uses.
He gave the specific example of Varget with 140-grain bullets in the .260 Remington. Varget wouldn't be the "best" Extreme powder to use with 140's. Instead the best choice would probably be H4350. In that application, he said, Varget loses some temp-stability.
I've used quite a bit of Ramshot TAC, Big Game, Hunter and Magnum when hunting here in Montana in cold weather, and all have done very well--as my chronograph tests indicated they should.
