I gotta good question for you guys. This has stumped me. Will guns work in space? If you guys want to throw any other epic questions out, go for it. All I ask is that there are no controversial questions, like something that would offend someone else. For example, the whole talk on religion and evolution. Don't want none of that right meow.
Bullets are sealed units, they don't require oxygen or pressure to fire so...yes. As to how the projectile would behave, I'd assume the lack of pressure and resistance would mean it would just travel for like...ever until it hits something.