Will a gun fire in Vacuum? Without oxygen or hydrgen etc.?

It will...

Bullets come equipped with their own fuel *and* oxidizer. No atmosphere needed.

Gunpowder is a mixture of fuel ( Charcoal and sulfur ) and oxidizer ( salt pewter ) so no oxygen is needed. However unless the gun was designed to operate in space, the mechanical parts would probably seize.

Note that a Gun was mounted on a Salyut space station and it was test fired once by remote control.

A modern gun (with self-contained cartridges) will fire - the oxidizing agent is with the powder.

An ancient musket or flintlock would not fire.

So there will be no ''Pilgrims in Space'' depicting our forefathers in steam-punk spaceships attacking space-heathens with their blunderbusses.

Until Hollywood decides that the story line makes it absolutely vital that Hester Prynne blast the intolerant and rapscallion space-mutants with her repeating flintlock of doom.

Now I'm going to have that mental image stuck in my head for the rest of the afternoon.

Bullet contains two parts. First part contains lead shot. Second part contains shell filled with gun powder. When bullet is fired the gun powder drives the lead shot with intense forward thrust and velocity. Bullet travels in vacuum also.

Yes. Bullets contain their own oxygen, and don't need any from the atmosphere.