^ Not explosive. You do need to purge the cylinder of air however because otherwise the pressure will prevent the reservoir from accepting CO2.
You will need to significantly reduce the hammer strike, otherwise it will waste CO2 on a staggering scale.
Energy will be only roughly half of what you will get from air at equivalent pressure, and because CO2’s operating pressure is much lower than the usual fill pressure for air, that will further reduce the energy to somewhere closer to 1/4. But shot count can be huge if it’s tuned well...that’s the advantage.