Note that it has been shown that at the point most obstructional bursts occur (12/20 combo etc excluded) "IF" the pressure were raised uniformly for the length of the bore behind the obstruction the barrel would contain the pressure without bursting or bulging. When the charge hits the obstruction it is checked in its acceleration down the bore & a pressure spike occurs at that point, not over all the bore behind it.
The fact of the bulge occurring ahead of where the wads were in the cited instance was because the charge was "Checked", not stopped. Velocity was high enough that it moved that far before the pressure hit its peak.
It has also been well proven the obstruction does not have to be solid, it's the weight that matters.
As to the matter of Damascus vs steel, & I love Damascus, its the yield vs tensile strengths of the barrels that determine a bulge or burst. As a general rule steel has both higher yield & tensile strengths than Damascus. Thus any pressure which bursts a steel barrel would burst the Damascus as well. Normally the range in which the barrel is bulged, but not burst is wider & starts lower for the Damascus. This does not prove the Damascus superior to steel, but actually the opposite.
