As with many brand loyalties, people tend to get a little carried away on both sides. i.e no one in his right mind can objectively state that .50 bmg pressures CIP max 54,000 psi is OK in ANY revolver chambered for .357 saami max 35,000 psi. That is just foolish hyperbole.
Ruger DA revolvers began developing a well deserved reputation for FRAME strength with the advent of the frame designs for the Speed and Security Sixes due to a revolutionary new frame design that did not include a side plate that accesses the lockwork. Colt and Smith had set the previous standard for DA frame design that included such plates and the plates weaken the strength potential of the frame.
This did not mean that the side plate frames could not be made strong, indeed there are expert opinions that the Colt Mk III revolvers of the late '60's and forward were the strongest revolvers of their time. They were contemporaries of the Ruger "Sixes".
Ruger was an innovator and that extended to a design decision to innovate a method of investment casting that is widely respected. This was for cost reasons and not that anyone believed that the cast steel was inherently stronger than forged. It did lead the Rugers to be chunkier and more massive in certain dimensions than the forged counterparts as evidenced with the GP100, Super Redhawk, SP101.
The cylinder is a key area for handling high pressures and strength (as opposed to simple hardness which is NOT the same) here is determined by metallurgy, heat treating and importantly whether the exterior cylinder notches are aligned with the thinnest wall of the chamber where it is closest to the cylinder outer wall. If the notches are aligned with the thinnest wall (closest to chamber) or offset from them determines cylinder strength as much any other factor. Ruger also pioneered offsetting the notches, but this is also a feature of other revolvers (i.e the S&W 686+).
Rugers are not Superman and they don't defy physics. I HIGHLY doubt than any expert would expect a Ruger with an obstructed barrel to allow you to fill up the barrel with bullets with no adverse consequences. That expanding gas is going somewhere and Ruger barrels are not magic.
Another source of the Ruger mystique came from the design of their Blackhawk SA revolvers, that externally seem similar to old Colt Single Action Army revolvers but are actually a much stronger design. The Colts were designed in the 1870's and have known weaknesses that were not so much an issue with the black powder cartridges of the time. With the advent of newer technologies it became possible to create loads in popular single action ammo such as .45 Colt that clearly exceeded the strength of the old Colt design but were fine in the Blackhawks. These new rounds are termed Ruger only adding to the perception of Rugers being somehow indestructible.
The bottom line is that yes, the SP101 is plenty strong for any ammunition that it is designed for up to the maximum SAAMI pressures, but it is NOT indestructible and no gun is. It is also not true that it is the ONLY strong gun. Unfortunately, to this date any attempt I have ever heard of to crown a STRONGEST champion has lead to highly dubious claims like this thread has, I hope they do not encourage foolish tempting of fate.
The rocking chair has probably found some cat tails here among those who cherish the mythical proportions of Ruger strength so I will get off and let them wail.
