I'm a total research monkey- comes of the whole 'being a writer' thing, I think.
Reading SAAMI's website (my God there's a lot of information there) their specifications for cartridge pressures are designed to try to insure that using ammo made to their maximum recommended pressure will not result in a catastrophic failure of ANY gun capable of chambering the cartridge provided that the gun is manufactured for that caliber. Given that cartridges have very long lifespans many calibers are rated significantly under the maximum safe pressure that will cause a catastrophic failure in even the oldest, most poorly made guns it is likely to be used in.
Given that many damascus shotguns are Nitro Proofed and were even more common at the time the standards were established it is reasonable to conclude that any standard pressure round will not cause a catastrophic failure of the chamber or barrel of an 'as manufactured' gun in good condition.
That being said it doesn't mean that a steady diet of modern high-pressure loads is a good idea. The use of high-pressure loads in any weapon will accelerate wear even in a modern weapon of good quality. The barrels are also not the only concern; the frame can stretch, the locks can be damaged etc. Modern loads may be 'high pressure' for old guns even if they don't blow them up.
All in all I'll err on the side of caution and rely on the experience of you good people when I 'come over to the dark side' and get my damascus gun.
