Here's the longer version Todd
A Parker GH with Damascus barrels and the Parker VH with Vulcan Steel barrels were the subjects of destructive studies in the
Double Gun Journal Vol. 10, Issue 4, Winter, 1999, “Finding Out For Myself” Part II
A GH with Damascus Barrels was tested till destruction. The gun was described as a ‘Wall-Hanger’ having pitting throughout both barrels but none dangerously deep with several small dents near the muzzle.
The loads were started at 1,254 FPS and 11,900 PSI (400 PSI above the modern SAMMI maximum pressure for a 12 Ga.). The loads were increased in approximately 2,000-5,000 PSI increments. At the 25,000-27,600PSI range (approximately 6,000 above PSI the SAMMI Proof Pressure of 19,500 PSI), the brass shell heads started to show signs of overstress: head flattening, extrusion into the extractor slot and cracking. The chambers and barrels showed no signs of expansion or of over-pressure at these pressures. The left barrels’ chamber opened up at 29,400 PSI and the right barrels chamber opened at 31,620 PSI.
There were no signs of flaws in the newly exposed Damascus edges such as rust in the welds or inclusions even though the barrels were pitted. The failures started at the breech between the barrels, where the walls were thinned before assembly to narrow the breech width, and in which a horizontal hole is bored for the extractor guide pin, making this area considerably weaker than other areas of the breech.
and Vol. 16, Issue 2, Summer 2005, “Finding Out For Myself” Part IX
A ‘Vulcan Steel’ barreled Parker was tested to failure. The gun was similar to the Damascus barreled gun tested to failure in “Vol. 10, Issue 4, Winter, 1999, Part II”, above. Both were built on a No 2 frame so they likely had similar wall thicknesses (it wasn’t mentioned), they had close serial numbers and pitted barrels. (Both also had flaws that took them out of the collector category, so the loss of a irreplaceable gun would be lessened.)
Testing commenced with Proof pressures, which showed 1,485 Ft/Sec and 18,560 PSI in the test barrel. The pressures were raised in approximately 3,000 PSI increments. The first signs of stress occurred at 27,620 PSI and 1,734 Ft/Sec when the top rib extension raised up and the barrels started to come of the breech face. The next load, 29,620 PSI and 1,748 Ft/Sec, showed the first damage to the Barrels, stretching the chambers by .009” (that is it was enough pressure to exceed the elastic limit of the metal, repeated firing at this pressure would eventually lead to Fatigue Failure). This is the load that blew the left chamber of the Damascus barreled gun.
The next load at 31,620 PSI and 1,801 Ft/Sec blew both chambers of the Vulcan Steel barrels. It is the same load that blew the right chamber of the Damascus barrels.
The Metallurgic Failure Analysis of the two barrels was posted on a public internet forum by 'Zircon', and reproduced here
http://www.shotgunworld.com/bbs/view...34280&start=20