How it works and what are the most important parts inside?
An airsoft gearbox is a mechanical shell that houses the inner workings of an electric airsoft gun (AEG) powered by an electric motor and a battery as the power source. It is placed in the lower receiver of the gun and attached through the motor grip and buffer tube bolt at the back of the receiver and a series of pins depending on the gun style. There are nine types of gearboxes found in various models of electric guns each one with slightly different inner working components. These gearboxes typically have three fire modes with variants having up to five, the most common being safety, semi-automatic, and fully automatic firing with variants including 3-round and 6-round bursts. Their main function is to cycle a piston inside the gearbox with the pull of the trigger to push a nozzle that shoots a stream of air through the hop-up and propels airsoft pellets through the barrel.
The most common gearbox used in most electric airsoft guns is the version 2 gearbox. The very first iterations of these gearboxes were created by the Japanese toy company Tokyo Mauri in 1992, later modified by various manufactures around the globe while keeping the Marui specifications the same. These gearboxes are typically found in m4/m16 style airsoft guns and have had various variants through its history. The AK47 replicas are using the V3 gearbox. Typically, any airsoft gearbox has around 20 components and this is what they do:
The mechanical energy is transferred to the air system when the piston meets the sector gear. The air system turns this mechanical energy into pneumatic energy that shoots the tiny bb out of the gun. It's the combination of these two energies that makes the Airsoft Gun work.
A spring upgrade will increase your AEG's range slightly but will increase the wear on the internal components and shorten the AEG's lifespan in most cases.
When you pull the trigger, it pushes on the sear so it lifts off the piston. With the piston unlatched, the spring can expand out, pushing the piston forward. This quickly compresses the air in the chamber behind the BB, building up the pressure needed to propel it down the barrel.
A higher speed motor spins at a higher RPM, which in turn increases the cycling speed of the gearbox and the rate of fire of the gun. A higher torque motor spins with more force, which allows the gearbox to turn against heavier resistance from a higher tension spring which can increase the FPS.
This system then changes the way the current flows through the individual parts in the airsoft gun. The trigger contacts are only used to tell the switch to open and close, and almost no current goes through the contacts themselves. Greatly improves reliability, and it can improve trigger response and rate of fire.