As long as there is still liquid CO2 in the cartridge the pressure is calculated as:
p = p0 * exp(T/T0)
where p is pressure in psi, T is temperature (Fahrenheit), and
p0 = 314.04 psi
T0 = 69.64 F
And here's a link to a more accurate chart:
So, the CO2 cartridge probably has at least 800 psi in it at reasonable room temps. I'd be surprised if those gauges could handle that pressure.