It seems you have decided to start another thread rather than follow up on the one where we ask "why would you want to do this?"
But in answer to your specific question, even commercial units are rarely able to knock someone down on a limb shot.
And no, that design is completely NOT a stun gun. That's for the best, really. None of these home-grown plans should EVER be used on a real person. And if you were to carry them into a situation where you expect to use it for self defense you're likely to be extremely disappointed. Bring low-tech pepper spray.