A review on the physiology of Insulin like Growth Factor-I (IGF-I) ... by Debnath, Surajit / Advances in Environmental Biology.
The spring piston airgun generates power using a powerful spring-loaded piston that is housed within a compression chamber. Cocking the gun (using a break barrel, side lever, or under lever mechanism) causes the piston assembly to compress the spring. When the spring is released it pushes the piston forward compressing a column of air in the chamber behind the pellet.
Under pressure, the corresponding nominal clamping force is reached as a reaction force of the disk spring packet. To release the thrust or draw piston, a higher hydraulic pressure is required, which, up to a maximum value, is proportional to the release stroke.