It's an A5, so doesn't have a reg as such Neo. They operate at around 800psi, or whatever your bottle is kicking out.
BHP, have you been using the marker before without issues or have you just bought it 2nd hand?
Firstly, check that the velocity screw isn't in all the way. If its not that, strip it down and check everything is in the correct place and lubed up, including pulling the valve out from the power tube and check all o rings for damage etc.....replace as necessary.
Pm me if you have any more trouble.