When working up loads or sighting in for the first time each season, I will let any gun I'm shooting sit for a while before shooting an additional round. Last summer, on an 85 degree day in direct sunlight, I conducted a simple experiment just to see if a HOT barrel made a difference in POI in my blued Model 70 Classic Laminate in .300 WSM. I started with a clean barrel and got sighted in with two, 3 shot groups which took me about 15 minutes. The groups were typical of what that gun shoots with that load; 67.5gr IMR4831 and 180gr Accubonds (~MOA). I then immediately commensed fire on a new target, firing 15 rounds (of the same load), loaded one at a time, all in under 3 minutes time. The barrel was obviously too hot touch afterward but all of my shots were exactly where I wanted them and with the exception of two flyers (my fault), stayed under an inch and a quarter.