I have the same problem, ive tried every configuration possible and modified config files as all the "optimization" guides instructed, still cant go above 25fps, making melee combat with laggy zombies practically impossible. It makes me kinda sad that you cant see any efforts of optimization on the development roadmap, meanwhile they keep adding hats, the game keeps being unplayeable for a lot of people. My Specs CPU: Phenom II x4 945 @3.0Ghz RAM: 8 GB GPU: R9 280x 3GB