shown is the firing chamber of the projectile gun with the bolt not shown is the controlling device the pressure measurement sensor 1 is the primary feature of this invention that differentiates it from other pneumatic guns no other paintball gun marketed yet uses any method of measuring internal pressure for use in controlling the velocity of the projectile the pressure sensor 1 is connected to the storage chamber 4 and measures the internal pressure of storage chamber 4 the sensor 1 then sends the pressure reading to the marker 39 s controller not pictured while a mechanical sensor and controller could be used the simplest implementation of this invention is to use an electronic pressure sensor and a microcontroller the storage chamber 4 is sealed by the use of two valves a firing valve 2 and an entry valve 3 opening the entry valve 3 allows compressed air from the high pressure storage tank 7 to enter the gun 39 s storage chamber 4 as storage tanks used for paintball are compressed to 700 psi to 4000 psi the air entering the storage chamber 4 will be at a higher pressure then any air inside the storage chamber 4 therefore the longer the entry valve 3 is left open the higher the pressure inside the storage chamber 4 will be this is the method this invention uses to control the operating pressure of the gun the entry valve 3 is opened and closed by the gun 39 s controller once the controller reads that the correct pressure inside the storage chamber 4 has been reached the controller closes the entry valve 3 the firing valve 2.