Bramble, Tinker, All,

I understand that barrels are not hardened, though they may be made of hard steel. Or, putting it another way, the barrels are not subject to a hardening process either before or after they are finished. Perhaps my understanding is incorrect?

Also, I am an executive of a company that welds, repairs, assembles, etc valving and piping in high pressure systems, mostly steam systems, from 1/2" through 36" and even larger, and at pressures of upward of 60,000psi. The systems run at various loads from long term full pressures to lower pressures to no pressure. Most systems are subject to anything from mild to intense vibration. I do know that rapid spikes, like a shotgun or rifle barrel would be subject to are to be avoided. Personally I don't know squat about the technical requirements of the welding, I got out of the hands on side of the business decades ago after a very short apprenticeship, but I'll ask some of our craftsmen, who are required to be certified by various testing agencies, about what is required to make the welds viable for the high pressures and able to stand the high vibration environments, which seems to me to be related to hardening and brittleness.

If I learn anything useful, I'll report back.

JPK