The governing equations for gas flows in 16-^m CO2-N2-H2 gasdynamic lasers using conical or hyperbolic nozzles have been presented in universal form so that for a given gas composition the solutions depend on a single parameter that combines all other parameters of the laser system. The solutions of these equations are used to compute the optimum values of small signal optical gain, and the corresponding optimum values of the area ratio, the reservoir temperature T'0 and the binary scaling parameter p'0L', which is a product of reservoir pressure p'0 and nozzle shape factor L', for a wide range of gas mixture compositions. The results are presented in graph form. An optimum value of 2.06% cm'1 gain has been calculated for the gas composition of C02:N2:H2 = 15:65:20.