OK, I'm going to take a stab at a plausible theory.
Decades ago, I was employed as a marine electrician, at Litton industries, Ingalls shipyard. I observed while doing ripouts on aging fast attack subs. A huge hole was cut through the hulls to rip out reactor. The pressure hull was chrome-moly eight inches thick. My uncle was the Yard Superintendant of machinists.
I was told that the steel used, was used for its property of elasticity, not hardness. I also learned doing a hot job on the USS Saratoga, the exhaust headers of which are made of CM, that CM has to be heated to almost red hot to be welded. That was what I was doing, monitoring the thermo-couplings. So CM has desirable thermal properties also.
The pressure hull has to go from sea level to a classified number of atmospheres of pressure, and back countless times reliably.
It's kind of a leap, but I think this property could have a reverse application. A rifle barrel has to go from ambient atmospheric pressure, to how ever many atmospheres all the CPU's convert to. Then it has to snap back to its initial state for the next cycle. It has to do this how many times?
Most earlier stainless steels were too brittle to be suitable for rifle barrels. I have a feeling considerable study was done on this modulus for specific properties and found some that worked.
I have rifles with both barrel types. My most accurate is a SS barreled Cooper MDL 22, 6.5x284, but I can't make a fair comparison, because my main hunting rifles are CM, Weatherbys, MKV and Vanguard are both, in my estimation are quite accurate.
The topic made me think about this, what think the rest?