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.
There are two types of piston engine that employ internal combustion: 'spark-ignited' (or SG) and compression-ignited (diesel). In spark-ignited piston engines, the air-fuel mixture is injected via a spark plug at the top of the cylinder.