"Fires can't burn in the
oxygen-free vacuum of space, but guns
can shoot. Modern ammunition contains its own oxidizer, a chemical that will trigger the explosion of gunpowder, and thus the firing of a bullet, wherever you are in the universe. No atmospheric oxygen required.
The only difference between pulling the trigger on Earth and in space is the shape of the resulting smoke trail. In space, "it would be an expanding sphere of smoke from the tip of the barrel," said Peter Schultz an astronomer at Brown University who researches impact craters.
The possibility of gunfire in space allows for all kinds of absurd scenarios."