It's tech time with Airsoft Outlet Northwest as Jesse gives us three videos on KWA LM4 Tips and Maintenance. For owners of the GBB-R you can see how to fix the issue of bolt engagement so that the bolt catch can be be engaged more consistently. To solve the sticky piston, some modding will need to be done so that the piston will be prevented from locking back to the rear of the bolt. As for third fix, it's a hop-up chamber mod to keep it from getting loose in the future. Watch and learn: