I was taking a look at some of the files and noticed the symmetry problems too. It seems some of them are related to reducing resources as much as possible on models so they're faster. A few of the guns will have actual modeled details on the left side and then just a flat surface with textures to mimic detail on the right, since you only see the left side of a gun up close (1st person view). A bit lazy but I understand where they're coming from. Go figure, right?