Flick it with your fingernail couple times. Throw it hard against your bed couple times. Degass your gun screw it in and see if that manometer actually has 180 BAR in it if your gun shoots.
I have used gauges from FX, Huma, and Wika and all of them are hit and miss with accuracy. I recently bought a couple new FX gauges (the black ones) and they are actually on the money.