I hope its been a little entertaining and you have waited patiently, so here it is. But first a some info on the shooter. Master class in sporting clays as is his son who was present. Approx 60 years old. But the most important thing is I know and shoot with them and because he owned up to this whole situation, we get to armchair analyze it by letting me take pictures. No disparaging remarks about him are needed.
Shooter wanted to see if the LC Smith would function and fire before the sxs event started. He drained the shot only out of a pair of shells. Went to the practice field and fired both. Momentary lapse of reason on his part then occurred when he immediately placed a fully loaded round in the rh hand barrel and touched it off without checking the bore for the stuck wad. The stuck wad in the LH barrel was also still there at about exactly the same spot as the blowout. There ya have it. Watch out for yourself and keep an eye out for everyone else. Stay safe.