So what d'you decide about reasons of blowing the barrel?
Could someone summarize it to me, too much to read with my poor English.

From my observations of this photos I'd say something happened when shot just leaved the cone, that's why the pressure was high about 14,500 psi (1000 Bar). I saw the same cratered 209's, when my test ammo produced about the same pressure.
Obstruction just behind forcing cone I guess and character of bending metal in this particular place says the same.

Geno.