Would normal slug-throwers work in space (outside the confines of a ship’s atmosphere)? Surprisingly, yes.
It’s true that there’s no oxygen in the abyss of space, but the firing of a gun doesn’t depend on oxygen even here on earth. Or, rather, it does, but not on the oxygen in the atmosphere.
The ammunition used in a typical gun consists of a bullet (the part that actually gets shot out of the gun), a casing filled with gunpowder (or cordite), and an explosive primer. The primer is ignited by the mechanical action of the hammer hitting its firing pin (or, in a rimfire cartridge, of the striker hitting the rim); this causes the powder to explode, sending the bullet flying down the barrel of the gun and out into the world. The gunpowder and explosive material in the primer already contain all the oxygen they need; they’ll ignite and burn quite happily with no external source of 02. Consider how tightly a bullet is clamped into its casing – how would free oxygen get in there anyway?
Though it’s noted that extreme cold in space might affect the chemical reaction.
(via GeekPress)
Or alternatively, if the gun is exposed to sunlight for any length of time, it could become quite hot, well above the normal terrestrial range for gun operation. Should be OK but I wouldn’t want to test it.
Shooting in a vacuum and in freefall would considerably improve accuracy, though.
For the first shot, at least.