[kiru]

The point of having a high rate of fire isn't for you to hit hard. And if you are shooting at 270fps with 0.25 bbs you are probably using a m100 or equivalent spring which normally shoots about 300-320 fps with 0.2 bbs.

As for the g&p m120 motor from my knowledge is built for high speed (increased rof) and shouldnt be used with heavier springs over m110 or equivalent, otherwise you'll be stressing it big time. If you want to shoot with a m120 spring (380-400 fps with 0.2) or above you may want to consider using a high torque motor such as g&p m140 with high torque gear sets. As heavier springs will put more stress on your gears and wear them out faster if not meant for torque. Though you will of course lose some rof in the process. And your gear set is made for higher rate of fire and is not meant for pulling heavier springs like a m120. You can but you will be stripping those gears alot faster.

So if you want to shoot 350fps with 0.25s you may want to consider losing some rof and going high torque. Otherwise a m110 spring or equivalent would be sufficient enough for you and should work just fine with your current set up without making much change.