[yuhaoyang]

I had one before... You need a zero trigger, which you can swap with the stock one when it breaks, which it will, a new hop-up chamber and rubber, new inner barrel, and inner barrel spacers, a new cylinder and cylinder head, a few springs to vary the FPS, a new spring guide as well.
Also, since I have no idea of what the inner barrel length is, I think it's a proprietary length(correct me if I'm wrong), get a thread adaptor, silencer, and an extra long inner barrel.