Go to a quality 9.6v battery or downgrade the spring.
If you absolutely want to change gear boxes, the v3 king arms or LCT at airsoftparts.ca are solid. The only thing I'd do is change the LCT piston to the modify ultra piston.
BUT, since both boxes have m120 springs (400fps) you still might need to get a better battery.
Last edited by coach; February 28th, 2012 at 07:59..