I'm in Minnesota -- probably the best proving ground in the world for anything to do with cold weather. I hate it here, I'd like to leave, I can't stand it anymore; how the hell do you become a good shooter in this sort of climate... :evil:
Oh oh, I see I've drifted off the point a bit. Anyway, it seems to me that the wad used is more critical than anything else. I continue to load 12 gauge, 1 1/8 oz. loads with International Clays (a little slower powder) even in the winter. I've had trouble (light report, lots of unburned powder in the barrel) using the PC Post wad (the new ones) and a friend has had trouble with Windjammers. But, I've never had any problems when using Winchester WAA12's, even with the slow powder. I suppose wad manufacturers try to build product for use in extreme climates, however, no one who doesn't live here can even imagine what hell the Minnesota winter truly is!