My 4 wheel bud works for General Dynamics who makes gun powder under the name you might know, Saint Marks in Florida. You probably are using some of their product and maybe don't know it. Per him, all powders are are temperature sensitive but it depends on the cartridge, shape of the powder granule and the detergent used to make it insensitive. The most insensitive to temperature will be of a tubular shape so that the surface of the granule can be coated with more detergent. Once the process is finished, the powder, as long as it stays dry, will not change in sensitivity. Heat, cold, doesn't bother it and neither does abrasion, as in, riding in the back of a 6x6 for a thousand miles. Depending on the cartridge, some are more cost effective to use a ball type powder which is why you'll see a significant amount of powders that are ball configuration yet insensitive to heat/cold. In chatting with him, I got the impression that our smaller cased ammo was more cost effective for ball powder vs powder for a 16" gun on the Iowa class battle ships.
That's what I was told when I asked....otherwise, I'm dumb as a fence post about it.
A few of St Marks powders:
They make 120 different powders at St Marks. A lot of it is for the military.