Weapon recoil as spring?

I was reading CryEngine's codebase, and specifically, the procedural motion bits in the weapon module: https://github.com/CRYTEK/CRYENGINE...628643917c820/Code/GameSDK/GameDll/Recoil.cpp

Their recoil implementation is very interesting. It seems to be some sort of spring, applying the effect on the world position of the weapon model (and arms). No IK, no bones, Seems to be the whole object. Does anyone have any material on this subject? Or is this very unique? How everyone else is doing this?

I'm very curious about this kind of thing. They also seem to add a jump bump motion procedurally, as well as sway and movement, but I still haven't found those pieces of code. I'm suspecting a classic Lissajous curve.

 

Bump?