As said, nail guns feed and fire the piston in the same motion, so any 'misfire' won't advance the belt and those empty gaps won't get progressed. Further as a safety issue built in to nail guns they won't fire unless the head is depressed. You won't hear the piston fire, instead you will either hear nothing or a small vent of pressurised air. What DOES get me though is the sheer number of "fires", the gun is still firing the same pressure despite no compressor kicking in to repump the tank. A framing gun like that uses a fair bit of pressure and works best around 100psi. Further the impact in which it's firing into the wood I would conclude they have the pressure regulated down very low (less than 50 psi), as at full pressure even with a steel table the piece of wood wouldn't just sit there like that. With the pressure that low the nail would still penetrate skin but wouldn't go anywhere near penetrating his hand.