Left handed weapon model bullcrap

I’m trying to port a CSS M4 to a source mod called “Empires Mod.”
But the M4 and almost every other weapon from CSS turns out left handed when I port it.


This is the where the M4 originally from: http://www.gamebanana.com/skins/79161

I tried to mirror the model in 3ds max, but the bones keep getting screwed up.
Is there a plugin for 3ds max or something that mirrors bones correctly?
Does anyone have any solutions to make it right handed?

Are the original weapons left handed? If so. Look around the options menu a bit and you should find one of those options that change wich side the viewmodel is mirrored.