Although in theory, black powder could be made to ignite if enough pressure was developed in the barrel during ramming the ball down on the powder, it is extremely unlikely.
The heat in this case is developed because of the compression of the air in the barrel, similar to the heated air from compression in a diesel engine.
In the case of releasing previously stored gas like letting some of it out of a CO2 cylinder, the reverse is the case.
The heating was done at the factory when they were pumping the gas into their tanks. There, it cooled before being placed into the CO2 cartridges.
When this compressed gas is expanded when it is released, it absorbs heat so, using a CO2 cartridge to blow something out of a barrel will chill the barrel and everything else it contacts in the area.
The heat in this case is developed because of the compression of the air in the barrel, similar to the heated air from compression in a diesel engine.
In the case of releasing previously stored gas like letting some of it out of a CO2 cylinder, the reverse is the case.
The heating was done at the factory when they were pumping the gas into their tanks. There, it cooled before being placed into the CO2 cartridges.
When this compressed gas is expanded when it is released, it absorbs heat so, using a CO2 cartridge to blow something out of a barrel will chill the barrel and everything else it contacts in the area.