I dont like to wait a long time between rounds at the range. I usually fire three shot groups about one minute apart. How much variation in velocity (over the normal standard deviation) do you get when you shoot this way? How much difference in group size does it make in a typical 270 or 30-06 sporting rifle compared to waiting 5 or 10 minutes to let everything cool off. For the sake of comparison let's consider were talking about a 70 degree day, not when its 25 below.

For very rough numbers, figure about 200 PSI and about 10 fps for each degree F of barrel temperature.

Elkhunter,
down here where the temp last weekend was in the 80's, you'd be hard pressed to use your technique. I can generally get two to three shots in w/ a minute between them (time enough to spot the round, mark my target sheet, and record the velocity), then I must wait for about five minutes and fire another two or three. Generally, I take at least two rifles, and I still must wait between mini-strings.

I pray for temperate weather, a good breeze, and keep the rifles out of the sun, bolt open, and vertical to maximize exposure to the breeze

I try to minimize the time the round is in a warm chamber, but have no doubt it makes a difference if the powder warms up. Kudude

PS: Love Big Sky and the Big Sky Country. I'd love to be up there when our temp is 100 in the shade and there is no shade!

We can get the 100's on occasion as well. But we are lucky enough to not get the high humidities.