So when a brass case is ejected from your action, carrying with it the heat energy from the fired round, it should be actually cooler than a steel case. But in actual practice, I believe that both are equally hot, meaning the brass case is carrying more heat away than the steel case. Brass is better here in that it ejects more heat energy away from the gun. What about plastic cases? They carry away almost no heat energy when ejected, letting the gun get very hot indeed. VERY BAD FOR THE GUN!