Is possible shoot a CO2 gun without CO2?

Answer 1

They can run, or be modified to run on High Pressure Air or "nitrogen" but they still must use a propellant of some kind.

Answer 2

no, but most guns allow you to use most types of air unless the tank doesn't fit.

Answer 3

It is fine, it does not do anything to the marker and dry firing (with co2 but no paintballs) does nothing that normal firing would not do