A couple of additional points for whatever contributing value they may have.

Ref: pressure. Someone on the 16ga forum in discussing this event stated:
I had Tom Armburst test some Factory Herters 1oz #8s a couple years back Fps right around 1200 , psi right at 11500 .

And, also, again a 2 3/4 shell in a 2 9/16 chamber.

Regardless, glad no one was hurt.
Sorry he lost his Smith.

Speude Bradeos