A CO2gas‐dynamic laser (GDL) was operated over a range of reservoir pressures and temperatures, test‐gas mixtures, and nozzle geometries. A significant result is the dominant influence of nozzle geometry on laser power at high pressure. Results show that high reservoir pressure can be effectively utilized if nozzle geometry is chosen to efficiently freeze the test gas. Maximum power density with the least efficient nozzle was 3.3 W/cm3of optical cavity volume, whereas 83.3 W/cm3was attained with the most efficient nozzle.