When it comes to gas powered Airsoft replicas the loading nozzle, or nozzle, is a component that serves to pick up BBs from the magazine, to insert into the hop up chamber during the cycle. The also serve the secondary function of acting as a channel by which to direct the flow of gas from the reservoir into the chamber.
Inside the loading nozzle is a spring loaded valve that is designed to regulate the flow of gas. This part can be tuned for different effects to the cycle, efficiency, and power output of the replica. However balanced tuning with other parts of the gas system is need for best effect.