We have built this spring in our CS-18. At first it went well. Top shot strength compared to the original spring. Unfortunately, I realized that are not optimal, the dimensions and / or the production quality. After putting on the black end member (do not know how it's called) could not be stretched because the piston blocked behind. Without the part, the weapon worked again. I have screws removed and found the back of the moving piston pushes the housing apart. It also could no longer squeeze. Here does not seem to be enough space with the new spring. But this can not be the solution. Too bad.
