I recommend changing the spring at this point, but that decision is up to you. When you use battery packs with higher voltage, it will increase the firing rate, but not the strength of the shot.
In my opinion, a 5 kg spring works best (the original one is a two kilo spring). I tried a 7 kilo spring in one, and although it was strong, it resulted in a lot of mis-firing.
To replace the spring, follow these steps:
Remove the collar and spring from the plunger (as shown in the third picture). Carefully remove the plunger. Pull the plunger out of its casing. After unscrewing the screw which is holding the plunger head you will be able to change the spring.
- Start by removing the orange plastic piece on the plunger.
- Remove the 10 screws marked in the first picture of this step.
- Then take off the casing.
- Unhook the spring.
In the last picture you can see how the firing speed improved. To give you an idea of the gun’s speed after the replacement - it is about as fast as an unmodified Nerf Maverick (so it is more fun, but not dangerous).
I tried to remove the air restrictor, too but noticed no difference in the firing speed, so I just left it where it was originally