M4/M16 Flat Top Upper Receiver Assembly for M4 / M16 Series Airsoft AEG, Accessories & Parts, External Parts, M4 / M16 External Parts, M4/M16 AEG Receivers - Evike.com Airsoft Superstore
Gearbox rear pin rotates when I try to unscrew it , I've tried pliers but it doesn't look like its working , and my gun is sad becuse it hurts : r/airsoft