I had an experience with H1000 in my 28 Nosler, received my rifle first of October, I live in Northeast TX, and this was like the third batch of reloads I had going looking for better groups, it was hot that day right at 90, in the afternoon no shade my ammo box open the sun beating down on top of me and the equipment. The first three shots all work good, not a hot load by any means when I loaded them, but the next round after they had been exposed to the sun for a little while had a more considerable kick to it and the bolt was stiff. I thought this is odd, did I just miss throw a charge, fired the next round, same thing then it dawned on me when I picked up another round, this is sitting in the sun way too long.. I covered them up and put them in the shade of my pickup and after 20 minutes back to normal pressures.. I wonder at what temperature are the temp stable powders really tested at, I have never investigated how they measure or test but I know from experience, even with H1000 being temp stable, do not expose them in the sun for very long.