I have blown up a lot of revolvers in testing and tried to blow up a lot more.
The failures I see in strength:
1) Cylinder splits in two or three pieces.
2) Cylinder splits in two or three pieces as the primary failure and the top strap breaks as a secondary failure.
The Ruger SS has chamber walls 0.080" to the outside with an internal diameter of 0.382". A rough hoop stress calculation for RC30 would indicate possible yield at P = 2 S thickness/ID = 2 140ksi .08/.382 = 59kpsi
And they are always much harder to blow up than calculated.
Compare that to a 357 mag S&W 640-1 with 0.048" walls and ID of 0.381". That could fail at 35 kpsi, but they are harder to blow up than calculated.
John Bercovitz wrote this in 1991 about the real limitations of the 357 magnum:
https://groups.google.com/forum/?hl=en&fromgroups#%21msg/rec.guns/S_dalM1NJe0/cBSU4bR2jz8J
Saving you the time of reading John's post, the sticky cases will be found at a higher pressure in the Ruger SS than the J frame, as the walls are thicker and so less stretchy.
The real limit of 357 mag is sticky cases. Sticky cases are the pattern of arrows shot into the fence. SAMMI registered pressures for the 357 were just the target later drawn around the arrows.

What does it all mean?
The Ruger Security Six in a work up will get hard to extract brass long before the cylinder splits because it is stronger than it needs to be.

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