If the gun uses this mag, it most very likely uses the same rocket valve/adjustable valve as the WA M4 GBBR system, since the nozzle has to be at the same place and the same shape.
But you could drive to a store that sells the gun you want (in the states) with a battery Dremel and cut open part of the rocket valve. Don't forget to buy replacement too.
GBBs can be boosted in FPS by allowing more air through before the blowback cycle.
Also:
http://shop.ehobbyasia.com/gandp-har...wa-m4-gbb.html