Not sure why you would bother asking about testing loads with a cold barrel. I doubt you are that ____. I can't fill in the blank around here. So you have another reason I guess.
I could copy what I do from national benchrest shooters site or XXX shooters, and some ladies would not like that. They should use their own methods. All I said was let the barrel cool, which is nothing shocking. If anyone says it is they are lying to themselves.