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.
Power Springs. In most cases, power springs, also known as clock springs, are made of pre-tempered high carbon steel or 300 series stainless steel. They also have either special retaining holes or bends on both ends. Because the material is pre-tempered, only the first few inner coils retain their shape.