As for the beating of this dead horse, the accepted rule is action open until it is your turn to shoot. To me, this point in time comes after the previous shooter has called and shot their bird. The timing is the same for pump, semi and hinge shooters. Shell in the chamber, with the chamber open, impatiently waiting to miss my next target.
As for AD's, the only one I have seen was due to a semi that slam fired when the action closed. The gun was taken in for a check up immediately to a smith, but no fault was found. It was suspected that the primer was not seated deep enough on a reload. The hull showed an extremely light primer strike, on a distended primer. Because proper safety precautions were being observed, the AD was in a safer direction, and no one was hurt. Lucky for us, out trap house is made of cement, and no damage resulted. We have not painted over this shot pattern on the house as a reminder to practice safe handling techniques.
It does happen, even to experienced shooters with well maintained firearms.
As for the guy who dropped his trap gun, whatever you do popcan, don't lend him your guns.

He should not have been eating buttered popcorn on the line anyhow.
I will go back to resting my muzzle in the dirt now. I had no idea that an open chamber was so dangerous to my toes.

Dragging the muzzle over the cement is much better.
Methinks David Doyle has not shot a 600 or 700 target weekend before. The rest is a must.