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.
Not all springs work by stretching and squeezing pieces of metal. An entirely different design involves using a piston that moves back and forth in a cylinder of fluid, a bit like a bicycle pump that's very hard to push in and out. Read more about these in our article on gas springs. What are springs used for? Photo: The mainspring from a clockwork toy. When you wind up the toy, you compress the spring into a much tighter space to store energy that's released when the toy starts to move.