charge 14 in another embodiment of the present invention perforating gun 10 may include mechanisms for reducing both the temperature and the molar density of the post detonation gun pressure one example is combining features disclosed in fig3 and 4 an example is illustrated in fig4 a it should be realized that heat sink material 16 and reactants 24 can be incorporated into perforating gun 10 of the present invention to reduce the post detonation pressure of the perforation operation the post detonation pressure may also be reduced by mechanical means which heretofore have not been realized when an ideal gas expands isenthalpically i e u201c throttling u201d the ideal example is expansion into a vacuum the gas does no work and possesses essentially the same energy after expansion as before if the gas 39 s specific heat capacity is constant this expansion is isothermal from the ideal gas law p r n v t such an expansion would only reduce pressure by reducing molar density p 2 p 1 v 1 v 2 here n is constant and v changes in contrast with the previous embodiment illustrated in fig4 a 4 b and 4 c however when an expanding gas does work it is giving up energy to the surroundings on which it is working energy conservation dictates that the expanding gas cools when an ideal gas expands isentropically its pressure drops as follows p 2 p 1 v 1 v 2 u03b3 wherein u03b3 is the adiabatic exponent approximately 1 4 for air and many.