7828 has been temp stable in my 300 WBY for decades.
So you’ve actually chronographed it at both 30* and 100*? I know that twenty years ago when I lived in Alaska there was a 100 fps difference in velocities between 20* and 80*F under 120-grain bullets in my .257 Weatherbys. I just reduced the load a few grains when hunting in”hot” weather. I haven’t tested newer lots recently, but it has always been the most accurate powder with heavy bullets in two different .257s.
.
