Would a Jing Gong airsoft gun with a metal gearbox still be unreliable?

I've been looking at buying an airsoft gun that i can actually compete with, not just to screw around with a few friends. JG guns are definitly cheap enough, but from iv'e heard they're really unreliable. But to me, if i get one of the models with a metal gearbox, it seems like it should be plenty reliable.