What is the base temperature you're comparing the fps change from?
What base temperature? 88F to 40F.. 40F to 90F.... All shot over my Garmin with same loaded ammo in both conditions. I saw a 2fps per degree velocity change. Thats just for the CFE 6 ARC mentioned specifically above. Ive tested lots of different powders.
For example, exact same setup, bullets, brass, primers, etc for this 6 ARC rifle and testing. Same days, I tested AR Comp as well. I saw a 6fps change from 90F to 40F... AR Comp is some of the most temp stable powder out there..