In the Crysis 2 campaign you're given the chance to exchange the weapon you're holding for the same model of weapon whenever you find one. Why is this? Do the weapons wear out, or is there really no point to exchanging, say, one Scarab for another Scarab, for example?
You can exchange weapons only if they have different attachments or modifications.
So, a silencer attached Scarab differs from a Scarab with Reflex.
If you encounter the exact same weapon as the one you are holding, you will only take the ammo from it.
Weapons do not wear in Crysis 2 campaign or multiplayer.