Bad things will happen. CO2 is pretty inconsistent and is required to convert from liquid to gas. When firing quickly the co2 tends to stay pretty cold and has no chance to convert to gas. This causes liquid co2 to be sucked into the marker freezing o-rings and solenoids causing mega damage. In the old days to combat this the forgrips used to be expansion chambers, but they would cold pretty quick. My suggestion, buy a £30 3000psi air bottle and save yourself a head ache.