Originally Posted by timtom1
I've ordered a new spring the systema M100 for my new ICS M4a1 how do I change the spring myself?
- Take out your upper gearbox
- Open it
- Swap the old spring with the new spring
- Put it back together (ensure all pieces are in the same place)
Edit: here's a youtube video.
YouTube- ‪Airsoft ICS M4 Gearbox Assembly Guide by AirSplat‬‎
**FAST FOWARD TO THE 3:30 minute
mark to see the uppear gearbox assembly