The intention being to gain a recognizence that for every action there’s an equal and opposite reaction. The ejection of the bullet from the barrel of the gun cause an equal and opposite reaction on the mass of the gun self. Thus, ejection of gas from a container causes an opposite reaction on the container, vacuum or not, because gas has a mass.
However, in an airless vacuum, would the gunpowder ignite?
IDTS, so even if there was mechanical movement on the firing pin, you would have no ignition and the bullet would not move...?
I think even if, as another poster said, the gunpowder was “oxygenated” or there was “oxygenated fuel” because there is no air, there is no ignition, combustion and therefore no thrust in a true vacuum.
As this all relates to space travel, let’s not forget NASA has said they can “no longer go back to the moon”, they no longer have the technology to do so....
very weird.