Originally Posted by g`fry
They don't just toss a heavy spring in and then ship them out of China. They specifically engineer the gun to run at 400 fps, reliably. This is the same thing KWA does with their products. So when you replace the spring you're basically getting a fully upgraded gun.
Care to Elaborate? Tavors coming out of China are already shooting 380+ FPS. G36s are shooting 400+. I can't imagine the extent of the upgrades that are supposedly being done to Ares and KWAs for the Canadian market that they are now being considered "basically fully upgraded".