Anti-reversal latch

From Airsoft Community Wiki

The anti-reversal latch is a component of an AEG gearbox that prevents the gears from turning in reverse. This is necessary so that if the trigger is released in the middle of the firing process (while the piston is being drawn back) the piston remains in its current position rather than being allowed to travel forwards again (which could result in the loaded BB being fired unexpectedly).