Another point, for those who remember their school science, pressure IS heat! And, heat is pressure.
Note that the hottest rounds coming out of semi autos are also the highest pressures. Rounds from blow back guns are hot, but not burning hot. Move up to 35k psi like hot 9mm and its a different matter. Move up to the 55k psi rifle rounds and they are hotter yet.
No doubt other factors play their parts, but don't overlook pressure, AND, its duration as a factor.
Note that the hottest rounds coming out of semi autos are also the highest pressures. Rounds from blow back guns are hot, but not burning hot. Move up to 35k psi like hot 9mm and its a different matter. Move up to the 55k psi rifle rounds and they are hotter yet.
No doubt other factors play their parts, but don't overlook pressure, AND, its duration as a factor.