AIRSOFT ELETRIC GUN SIMULATION

Hello every one, does anyone know have any idea on how can i simulate this kind of compreesing and releasing of the spring that are shown in this video? I have all the paremeters masured, all the informations needed but I am stopped in the whole gun simulation simulation because I don't know how to simulate it.

Airsoft Eletric Gun animation Video - Youtube

If you want more information, just let me know!!