If this helps you to decide:
http://www.airsoftgi.com/product_rev...oducts_id=1844
In the reviews someone wrote
"paired mine with systema helical high torque gears and a
130 spring and a 9.6v and the the ROF is insane (side note the motor I replaced was a EG1300 which when paired with the same gearbox and battery is incapable of pulling the spring back)."