If you don’t know your way around the gearbox of a gun, send it to a tech and get it done properly.
If your techy, search YouTube for V2 gearbox disassembly and learn the components inside it.
Once you have done this and know enough, then you can understand why I have said this.
Once youve got got to this stage, if your still interested in upgrading the ROF you’ll get asked why, and what are you hoping to achieve?