Pin gun used to set off 9mm and .22 - pressure and physics

Uploaded for educational purposes. Pressure takes the path of least resistance. So not having a firing pin backed with a solid mechanism against the primer means the powder explosion pushes the primer out instead of pushing the more massive bullet out of the front of the cartridge.
The .22, not having a primer will push the lead out of the front. However, as is seen, since there is no solid firing pin at the back, the bottom of the .22 casing does rebound after it has been hit.
Original can be found on youtbe.