Originally Posted By Pakieser:
Most Japanese model guns use a "plug fire cap" system. You should be able to look into the chamber and see the firing pin. It uses brass cartridges. You unscrew the cartridge in the middle and insert a propritetary "plug fire" cap inside. There is also a free-floating washer which acts as a piston.
When the gun is fired, the hammer/striker pushes the cartridge forward against the firing pin in the chamber. The firing pin fits into a hole in the cartridge and the piston and fires the cap. The expanding gases from the firing of the cap push the piston against the firing pin, creating recoil that causes the cartridge to eject.
I had a few different PFC guns back in the 1980s, but they are long gone.
Found via Google - not the same gun, but a good example of the PFC system.
There is no pin in the chamber or the bolt. The gun release the hammer/striker only after the bolt is closed. It seems on full auto the sear is held back and the hammer/striker follows the bolt. Slam fire is more like it.