I know we've gone back and forth over this before:
https://pistol-forum.com/showthread....-bullets/page2
I tested Win231 at 40F, 70F, 90F while you tested at more extreme temperatures.
Working with a 135PF load (which is a good margin of safety for Action pistol) I think you saw a +-3PF variation with Win231.
This was contrast to my experience where there was no measurable difference.
Enos has a few threads about Win231/HP38
https://forums.brianenos.com/topic/2...e-sensitivity/
The reality, however, is that Win231 is a nice broad-use powder that, with a respectable PF loading should make it at all reasonable temperature spreads.