RL-15 was pretty darn temp-sensitive BEFORE the military chose it. Apparently the military's temp requirements were not being met by the original RL-15, but they got a chance to the improve performance. The "improved" powder was then accepted. (Or at least this is the story I was told with somebody who was fairly high up in the Alliant organization at the time.)
I have tested a bunch of powders in various temperatures and the present version of RL-15 is much than it used to be, but other powders have been more consistent in both cold and heat.
