As @vermithrax has said gun powder is part oxidizer, part rapidly combusting material. And so a gun will operate in space.

However, everything else is built on lies.

Everything you were taught in school, including science, is wrong.

Gravity operating as a force of mass attracting mass is a lie. Cavendish, an insane rich guy, did this crazy experiment in a barn... that has never been repeated.

Further, the electric universe model is proving far better at explaining the orbits of the planets and... everything. The entire debacle of "dark matter" being thought up to explain the lack of mass to explain the "gravity" model so that it would work across the galaxy is just ludicrous.

Also, it is beginning to appear that space is filled with a liquid. Only the area behind the sun is a so called vacuum. And the planets follow along in a vortex like spiral behind the sun as it clears the way.

Look up Kozyrev for more information