The pressure relief valve keeps the regulator from over-pressurizing. The regulator that's built into the marker drops it to 350 or below.
Originally Posted by Jay2014
Don't be super surprised if you can't get it over 270 fps on HPA.
There is a cure for that. You need a Ninja SHP tank regulator set to 950psi output. Ninja designed the SHP tank regs specifically to solve that problem in Tippmann markers.