This CO2 Charging Gun does not require pressure regulator. There is a very little need to regulate the suitable pressure for low and moderate power air guns that is within a temperature range tolerable to humans. The pressure of the vapor does not depend on the tank size but only on the temperature till some liquid CO2 remains in the reservoir. A small liquid volume converts to large pressurized gas volume which is a very simple system for storage of energy. Thus owing to the advantages, the CO2 Charging Gun is more simply constructed.