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.
The Feltenberger Pendulum Pump by Gravitational Energy Corporation, is a commercially available device that is manually operated and uses gravity-assisted power (GAP), coupled to a piston pump, capable of pumping and filtering 1,000 gallons of clean drinking water per hour.