I guess the simply example of this is the military. Their trucks sit out in temperatures that are all over the map. In Iraq the ammo sits in the sun and it must get to 150-160 degrees. Then in the arctic they train in cold temps. So why is storing powder in say 90-100 degrees bad if having the ammo, once loaded, in the same heat, ok. We all hunt in low and high temperatures, and we shoot in low and high temperatures. I dont see people carrying insulated ammo cans to the range and pulling ammo out one piece at a time. It would seem silly to me that theere could be a chemical reaction that only happens when the powder is in a plastic jug, and not loaded in brass.