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.
A gas spring is a type of spring that, unlike a typical metal spring, uses a compressed gas, contained in a cylinder and compressed by a piston, to exert a force. Common applications include automobiles (where they are incorporated into the design of struts that support the weight of hatchback doors while they are open) and office chairs.