Cant remember who told me-network 54 few yrs back ,if your Fx gun shoots better single shot than with the mag. only wind it once(watch spring in mag) after it passes the stop first time -My 25 mags were wound so tight they hurt my thumb-I always thought it was for the semi auto rifles -one mag.system for all. the one fault of doing this is if you drop your mag on the ground the lock pellet will fall out