Step 9: FPS Upgrade
A spring upgrade is the obvious way to increase FPS. Spring ratings can be found online, but I went from a 120 spring to a 100 spring in order to drop my FPS from about 390~ FPS to about 340~ FPS. An upgraded spring begins to stress nearly all the other parts of the gearbox.
2. Tightbore barrel
As I mentioned previously the difference between a stock barrel and tightbore barrel can be as little 0.04mm, however this difference can mean slight increases in bb velocity since there is less air escaping past the bb.
3. Associated parts
The spring upgrade is THE way to upgrade how hard your gun shoots. However the spring upgrade causes increased stress on all parts of the gearbox. You want the technical list? Piston, gears (Spur, Sector, Bevel), bushings, tappet plate, spring guide, motor, everything. Each of these may need to be upgraded in order to handle a stronger spring. Man, I've heard of people's entire gearboxes cracking under the pressure of ultra strong springs and internal stress.