Adding Weapons without Mutators

I've been looking into this for a while but something that I find frustrating is how even though certain weapons (hunting rifle & Moss 12), I can't use them in multiplayer. I read somewhere that this is because the server isn't running the mutator. What I'd like to do is add the weapons in such a way, that from the client side, I can use these weapons in any server I go to. (Why? Because why not?) I've yet to successfully do this and am beginning to wonder if it is even possible.



TL;DR: Add weapons directly into the source code without the need for a mutator and have it treat the addition like a vanilla weapon.