hey guys, i have a US SOCOM SCAR SOF combat assault rifle and a ECHO 1 TROY MRF-C, i was wondering what is the best spring or whatever to upgrade the fps/rpm and yeah i know the scar story and now it is like 500$ (yay!)
No matter what your goal is, you should be thinking on the key parts. Most key is the hopup. That is what you should pay most attention to. Two other things that are important is the barrel which needs loads of attention, and then you should consider to shim the gearbox properly to make it quiet and smooth.
Once you've got those things sorted out, you can start considering upgraded parts, since today most stock-parts are plenty good for a reliable rifle.