You are absolutely correct; fluid steel can also be damaged by excessive pressure. The tensile strength of fluid steel, for a given barrel thickness, and assuming modern alloys, has two advantages: raw tensile strength and homogeneity. Damascus steel yield strength is typically in the 7-800 megapascal range; modern steels go up into the 2,000 megapascal range, but could also be low, in the 500 MPa range for a plain carbon steel. Damascus steel is heterogeneous, by the nature of its construction from layers of dissimilar alloys. It is the dissimilar alloys, however, that engender the problem; I had a long discussion with an electrochemist about galvanic interaction at grain boundaries and micro-corrosion at the boundaries of the different steels, which weakens and changes the tensile strength of the material over time, when I bought my Barlow, in an attempt to determine the safety of firing it. In addition, hydrogen embrittlement, which can happen with all steels (hydrogen is a small molecule that can diffuse into steel at atmospheric pressure) takes place the more so in Damascus steel because of the presence of a greater number of microscopic voids and incompletely fused interstitial surfaces. Both electrochemical processes can give rise to internal stresses in the metal, which themselves spontaneously change its yield strength over time. Finally, there is no such thing as "Damascus steel" - Damascus is a process, not a material. It is not standardized, in the sense that the number and particular alloys of steel used, the forging temperatures, and the process can all vary from barrel to barrel, as well as between manufacturers. It's like saying that cats are nice; they don't all come from the same mold, and saying a tabby is affectionate has no bearing on the behavior of a leopard.
When Damascus steel is used in the creation of a black powder gun, with insight and testing, the thickness of the breech end of the barrel is designed, as I said above, for the stress profile of a black powder round. Peak pressure in a black powder round generally happens between 125 and 200 microseconds after ignition start; peak pressure in a smokeless round at around 250 to 400 microseconds, although it is highly dependent on the powder used, which is indeterminate a priori. That doesn't sound like much of a difference, but when you are accelerating the shot payload at about 3 to 5,000 G, the distance it moves in that time is significant. That means that the peak pressure may, or may not, move down the barrel away from the breech. If the barrel profile was not designed for that, necessarily it would be subject to strain - that is, exceeding the ability of the material to elastically return to shape. In a hybrid alloy, where internal discontinuities occur, that in and of itself can initiate failure. The difference with a fluid steel barrel is that in order for that to happen, you have to have an overpressure condition relative to its design strength; with Damascus barrels designed for the firing of black powder cartridges, you don't need an overpressure condition; you only need the pressure to be in a different area of the barrel from that for which the barrel was designed, which by definition can be the case for a black powder weapon firing a smokeless reload.
Obviously, if the Damascus barrel was designed and built yesterday, and specifically for smokeless powder cartridges, the above does not apply, since it would exhibit the excellent properties of high yield strength and elasticity inherent in steel made by the Damascus process. But a barrel made 150 years ago, of questionable provenance, fired with black powder loads and subject to uncertain cleaning and a century of salt and galvanic corrosion and micro-structure Hydrogen infiltration is one that deserves closer inspection than "Oh, them old Damascus barrels could shore take it." What motivated my comment was that in reading the posts, it sounded like posters believed that there was some "mystique" about Damascus technique that made it invulnerable to failure, which I felt was bad advice and a bad rule of thumb. As old as my hands might be, I like both of them just the way, and in just the place, that they are. So I posted a cautionary word to counterbalance the impression I got, out of a sense of responsibility. To your left hands.
As for the other good-natured cracks: no, I haven't visited this forum before under another assumed name. I share a number of commonalities with "George the Animal Steele;" like him, I have a bachelor's and master's degree, but not from Michigan, like him I was a track and field and football athlete, but it was my father who was a wrestler, not I. I have been nicknamed "the animal" (when I played football as an offensive guard and defensive end, because I broke so much of my equipment, including my helmet - which may explain a lot about my occasional incoherence), as well as Rusty, Stainless, and Remington. But I sure don't look like him. Sorry if my attempt to share advice I received in good faith from a scientist ruffled the feathers of the old-timers here. Peace.
