Alright, i've got a G&G m4 and i was looking at upgrading it for outdoor play. The stock gearbox is great, all reinforced and such so i don't want to fiddle with it. The only thing is it's shooting pretty low at 320 fps with .2's and i want more along the lines of 370 with .25's. Converting it into an spr, anyway i was online looking for a new gearbox that i can swap for outdoor play and i've come across a lot but i found one on velocityarms.ca. I think it's a custom built gearbox that is chrono'd at 400 fps for $70. The only thing is the parts are jg, now if i have to i will buy a systema gearbox but that alone with be $300 us, plus $100 for the motor and however much for shipping. What do you guys think/ suggestions? But i will say i'm not cracking the gearbox open to touch it, i want a new one.