This paper studies the possibilities of increasing the amplitude range of the generated pressure steps in the developed diaphragmless shock tube by using appropriate combination of gases in the driver and driven sections of the shock tube. The measurement results of the generated pressure steps using different combinations of lower-and highermolecular-weight gases as driver and driven gas are presented. By comparison of the resulting pressure steps generated in the diaphragmless shock tube, the most appropriate combination of the driver and driven gas for generating the largest pressure step amplitudes is determined and discussed.