I have been doing some shooting this summer with a 270 Win and a 308. The temps have been between 90 and 100 each trip. I shoot one shot and let the barrel cool for 2 to 3 minutes.....once a 3 shot group is complete I switch rifles or one of my buddies will do the same with his rifle(s).

I have found this to work good for me and it has produced consistent results with my rifles....which have sporter weight barrels. Must also mention that the bench and the area around it is shaded....so I think this helps both the shooter and the rifle.