What were the Halo 3 Guns modeled after?

[claire.linx]

Okay so I was playing some Halo, when I thought about like the sniper rifle, assault rifle, and the shotgun. What actual guns were these modeled after?
I was pretty sure there was some video out like a billion years ago (lol a tad exaggeration) about this subject...I was just hoping some-on remembered. =)
M203? I looked that one up, and its registering as a grenade launcher. umm n exactly like a Halo shot-gun...

 

[HaloKing Craig]

Most of the guns are like futuristic hybrids of modern weapons. I don't think that they are 100% influenced by real weapons though. This is a very unique question to research though!