Two things catch my eye on the Parker blow-out.

1.The original chamber/monobloc is still intact & the rupture starts at the sleeved tube parting line.

2.The end of the shell is well past the normal chamber length. I just measured one of my Parkers and the shell shown appears to be about 3 1/4" to 3 1/2" in length. Could someone have stuffed a 3 1/2" magnum 12ga shell in this one? Did the shell case separate from the base & get lodged causing a higher pressure?