Some powders like E-3 get faster with lowers temp most get slower like Clays, probably not enough to worry about unless you are going to a major match where they chrono. SO chrono as close to the match as you can with the same expected temps and add .1 grain so there will not be any surprises at the chrono. Different chronos can read slightly different. Keep everything the same, primers, bullets, OAL and crimp etc.....