would it be possible for a gun to fire in the vacuum of space giving that an explosion has to occur?

The powder in a bullet cartridge is self contained and pretty much air tight. There are TWO main parts to a bullet: The shell that holds the powder and the bullet or projectile. When the hammer of the gun hits the back of the shell where the powder is located, it creates a spark within the shell that ignites the powder. That is why a gun WILL fire underwater. The explosion occurs within the shell and the gas from the explosion forces the bullet out of the barrel. You should be able to fire a gun in space because the explosion occurs within the shell of the cartridge.

The smokeless powder that is used in modern firearms consists of nitrocellulose and nitroglycerine (plus bunches of other stuff). Both of these will decompose energetically without oxygen. So you will get the bullet to fire in space. Of course I am assuming that the firing cap will also fire, a safe bet, I believe.

What I do not know is what proportion of the gases produced are produced from the reaction of the above two constituents with oxygen.

My guess is very little, but I could be way off. I believe it is safe to assume that a gun would work in space, especially if it just entered vacuum. With time the oxygen inside the casing would leave, and so, possibly would other components. I am guessing that a bullet left in outer space for a while would fire but with less speed than a normal round - since the major reaction would be the nitrate to nitrogen decomposition without the carbon to CO2 and H to H2O reactions.

nitrate decomposes to oxygen and nitrogen so there would be some oxygen available, but my guess is the bullet would be slower and get slower with longer vacuum exposure.

If gunpowder needs oxygen to burn, then how do you think the oxygen gets into the shell and barrell when you fire a gun in the atmosphere? The powder is sealed in an airtight space, so it doesn't matter what is outside that space. All the chemical ingredients for powder to burn are included in the powder. If anything, the bullet will come out a bit faster in a vacuum because it won't have to push the air out of the barrel.

Interesting premise, but yes, the gun powder is a fuel. It does not need oxygen to explode. So it would explode... given that it would explode, and that the explosion will be contained, the container will be compromised at the weakest point or the point at which the bullet will come out.

All the guns can fire in space! But the one that holds them will start traveling very fast the opposite direction.

Yes that a gun would fire as it includes a source of black powder (saltpeter) which includes a source of oxygen. However no explosion.

Yes, because the gunpowder in the bullet will ignite causing an explosion propelling the bullet and the gun.

Yes, because modern gunpowders contain an oxidiser.

Yes of course.

Thrusters on rockets fire, stars explode.

seeing as its gun powder and how fast it burns, id have to go with yes. just a rough guess though.