Tinker,

You speak as though you have some knowledge of metallurgic issues. I don't know squat. I do understand what you have just described about metal failure, though. By inspecting that rip you can make a judgment of whether it was a failure that developed over time. That's just the type of info that would settle my suspicion of R-15, one way or the other.

On the testing issue, can you give some detail of what tests might be available, who does such tests, and what to expect in the way of cost?

There's a lot to learn here. Frankly, I would be more comfortable if the edges of that rip would show peening and corrosion. Then we could discount the possibility of a pressure spike. I too had wondered about the re-conditioning, and whether that could play a part in the failure.

Curl