Yea we run some full auto's...just not very often. Probably what you are hearin is 10-20 shooters doing rapid fire drills or double taps...something along those lines.
IIRC, you need to rack a belt-fed twice to clear it. You need to clear the round from the chamber, at which point the next round feeds from the de-linker into the chamber, and then you clear that one as well. From the ops story I gather that the bolt was only racked once, leaving 1 round in the gun yet. Also, there are no safeties on 1919's, and the trigger is very easy to "bump" while handling the gun, so I could easily see how this happened.[Monty Python]
It's only a flesh wound.
[/Monty Python]
I am not clear on exactly what happened just prior to the shot. I gather there was still a round in the chamber somehow despite everyone thinking the gun had been cleared? Did the instructor pull the trigger as he was putting the gun away, or did something mechanical set the gun off without human interaction? How is the instructor dealing with the aftermath of all this?
You are an extremely lucky guy! Best wishes for a speedy recovery.