What's the mechanism at the open cylinder end.
IMO the Failure Mech. at front of cyl. would be crevises in the ball... molding voids if you will. Or an undersized ball/oversized chamber.
Most critics and testers agree 90% of chain fire come from the rear...jus' can't be proven they are random mishaps no evidence left to prove anything, that's why they call happenings like this an accidental discharge. Most guys can relate to that.