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.
Pre-charged Pneumatic (PCP) Pre-charged Pneumatic Rifles, or PCP, are high quality, very accurate air rifles powered via a compressed air cylinder, which is built into the action of the rifle. The air inside the reservoir is pressurised up to around 200 bar (2900 PSI), and is refilled by means of a Diving Cylinder or Stirrup Pump.