I likely made this in one night in the late eighties with just parts I found in the garage. I had no real understanding of the dangers of mains voltage, and probably cut up a tent pole for the barrel. But I wired it to a 120V NEMA plug and to my surprise Mr. Vassos plugged it in untested at class the next day, I dropped a steel 10p nail down the barrel and it slid down to make contact with the back plate, then ZOT! the circuit breaker blew in the classroom, lights went out, and the nail shot out only a couple feet, bloop onto the floor. But it worked! You can still see the burn mark from the one and only test fire. Success! I got the extra credit.