A student in a CCW class if they could see my Wilson CQB, I drew it removed magazine, racked out the one in the chamber,and checked chamber, handed it to the student muzzle down, he then racked the slide, (from where I was standing, I could see the chamber and it was still empty) and dried fired pistol, he racked the slide again, but this time when he pressed the trigger it went "BANG" instead of click. Well we all jumped, but he did have it pointed at the ground it was nothing more than that.
So what happened? I'm pretty sure when I removed magazine, the top round peeled off, and was laying in the mag-well, and since we were keeping the muzzle down, it just laid there, after being racked a couple of times the round slid from the mag-well into the chamber, and at least "safe direction" saved us from anything bad happening.
After the class left I did try to repeat it, but couldn't get a round to peel out of magazine, and by just laying the round in mag-well, I couldn't get quite get the angle for it to "feed" into chamber, in 6 tries, I only got it to slide across the chamber, looking like a stovepipe. I guess the student was just holding it at an angle that allowed it to shimmy into the chamber
Sort of a perfect storm, but one that will not be repeated