When assigning a hiddenSelection for Weapons and changing their RVMats with hiddenSelectionsMaterials[], either the game does not load the RVMat itself or does not load the maps connected with. This means that none of the connected maps is beeing loaded, resulting in very bland looking weapons.
See pictures:
http://abload.de/img/2016-02-0120_55_01-gr4ypuz.jpg
This is how it should look. Notice the numbers stamped into the reciever cover.
http://abload.de/img/2016-02-01_00001c9qgx.jpg
This is how it looks ingame.