Gunpowder is used in all firearms. Blackpowder was the first rendition invented by the Chinese hundreds of years ago and was used in muzzleloading rifles such as the ones used by soldiers in the American civil war. Gunpowder does not contain any oxidizer, however the oxgen within the case is more than what is needed and the seating between the case and projectile is airtight. Hence also why guns can be fired underwater. Guns will work in a vacuum. And it is entirely possible to fire an automatic weapon single handed. however negotiating in the weightlessness of things, it would be easier to manipulate but harder to fire consecutive rounds due to the muzzle climb.
