In my cold-weather tests in the .270 Winchester with 150-grain bullets, made at zero Fahreheit, RL-26 actually chronographed slightly faster than at 70 degrees. (In the same tests, RL-16 and 23 also proved to be very temp-resistant.)
I haven't tried 26 in the 6mm Creedmoor yet, partly because I do a search of all available data when working with a new cartridge, primarily looking for the highest listed velocities, and 26 didn't turn up there. But RL-16 did, and proved to provide very good velocities and accuracy.
