Funnily, the guns in space has come up in current shows too lol
Okay, so I have a couple problems here:
- While your
weight is lower on the moon due to its lesser gravity, your
mass is still the same, and since he had the weapon (somewhat) shouldered it should not have knocked him back so comically, especially given the extra mass of his suit and everything on/in it.
- It's played for a joke, but no, you're not going to be able to fire a rifle bullet and have it circumnavigate the moon and hit you.
(They do actually do something smart by having the weapons painted white; with no atmosphere to cool the metal down, they could eventually absorb enough sunlight to get too hot to handle.)
They also covered one thing not mentioned, trying to actually aim while in a bulky space suit when you cant hold the gun sight properly.
You run into the same problem with firing while wearing combat gear and a gas mask. It's definitely not easy.