Summertime on the range
There's no way to defy physics - rapid-fire shooting drives barrel temperatures up, fast! Don't let your barrel overheat. Keeping your rifle in the shade keeps the sun from warming it. After leaving the firing line standing your hot rifle in a rack with the barrel up and the action open, creates a chimney effect, drawing cooler air in from the breech as hot air escapes from the muzzle. Together, these tactics will help your rifle keep its cool.
Sweltering summer temperatures adversely affect ammo performance. Some powders are less temperature sensitive than others. Still, it's best to take precautions when daytime temperatures are above normal (the temperature used when developing a load or testing ammo). Keep ammunition out of the direct sun - a range bag works well if there's no shade available. In scorching weather, consider a soft-side cooler bag with a freezer pack to give hot air the cold shoulder. When using a bolt gun, do not close the bolt on a cartridge until you're ready to fire. 'Cooking' a cartridge in a hot chamber increases pressure and will likely affect point of impact. When possible, it's a good idea to test your ammo in the conditions you plan to shoot.