I think that it will shoot the bullet to travel thousand and thousands of miles and then return again to the moon very slowly but the shooter will be also taken to space for a couple of maybe hundred or thousands of miles before returning to the moon. The bullet and the shooter will travel at a higher speed than on earth (the bullet will in both scenarios because the shooter on earth will be able to manage the backward force standing in the same place)

All of this is ever the gun fire after all. About combustion needing oxigen is a good question in the comics.

Not exactly. The escape velocity of the moon is 2.37 km/s, and a typical rifle muzzle velocity is around 1 km/s. So the bullet won't be able to escape the moon's gravity and enter orbit. Without doing the math, I would expect the bullet, if shot straight up, to reach tens of miles before returning to the surface. The shooter might be knocked on his/her butt from the kick of the rifle. But there is not even remotely enough energy to do more than that to the shooter.

Will the gun shoot? Well, the oxidizer for the reaction, the explosion, that propels the bullet is in the powder. The question is at what temperature the bullet might be at. In the dark, the bullet might be at -300 degF, and the powder reaction might not happen. In the sunlight, the bullet might be heated enough to burn the powder. Lot's of 'what if'.....

Della, I stumbled across this:

If you fire the bullet on the moon you are basically in a vacuum. The friction of the moon's atmosphere will be negligible but will eventually act against the bullet enough to slow it down - unlike the bullet in an ideal vacuum that goes on forever. Depending on the velocity of the bullet, it may impact on the moon, it may go into orbit, or if it is going fast enough (faster then the escape velocity of the moon) it will break free of the moon and go into its own orbit around the earth or sun. Since gravity is much less on the moon, the bullet will travel much further then on the earth before it impacts the surface.

DIsregarding the curvature of the surface of the moon at all (and vs. on the earth) and the loss of velocity due to friction, the bullet will be pulled 'downward' due to gravity at a slower rate then on earth - roughly six times slower. So the bullet will go about six times as far.

So you're saying that the gun would actually fire, and that the lack of atmosphere wouldn't inhibit the gun's ability to fire? Or, does the kid get it right when he says that the bullet casing creates its own atmosphere?

That just doesn't sound right to me. But I truly don't know...

I appreciate your responses and am looking forward to more.

Cool, Jacquin! So, someone really has asked this question and come up with an answer?

I'm glad to know that...it's been bugging me since Sunday!

There were two questions:

1. Will the gun fire? combustion needs oxygen. Answer: yes, it will fire. Gunpowder has its own oxygen mixed in (oxidizer). A gun will fire under water as well.

2. Will the bullet travel farther than it does on earth. Answer: yes. Four factors determine how far a bullet will travel: air resistance, muzzle velocity, angle, and gravity. Discounting air resistance, the difference in gravity will give the bullet a 6X advantage, and add some additional distance due to lack of air resistance.

Yes, I was thinking about it after I post my comments and I realized that the bullet might actually escape the moon gravity and start orbiting the moon or attracted by other planet where it could start orbiting. But the question remains if the bullet ever fire which as you said it might not happen.