Save Hong Kong!
I also found if you fill that slot with grease it will help prevent that sucker from flying off
Swiss Arms PE-90. Owner
Ive found the grease helps in keeping the spring in place, but also attracts a lot of debris from the blowback action.
I have been cleaning mine every outing so have not faced an issue yet, but can see it being a problem at some time.
"If you teach your kids how to shoot, when to shoot, what to shoot, and where to shoot, freedom will easily be maintained." - Erin Canales