I am quite sure that you are not allowed to use those meshes from Valve. You can create a MOD in the source engine. But you should read the license. Artworks are not allowed to use outside of their games.

Better make your own meshes. You learn better how to texture and unwrap.

By the way: the weapon cylinder at the front gets light from top and bottom. Strange.

Models, Textures and Games from Dexsoft