Do we have any numbers that we can use for calculative purposes; elongation, tensile strength, ductile strength etc? For instance a 12L14 hot rolled number of 22 is a nice number to have, but what does it mean when it comes to strength?
In the context of this discussion, the thinnest point of the dovetail will be the weakest point. But, because of the high elongation factor the thin area can "borrow" some strength from the surrounding metal on either side of the thin area. At the muzzle it can't, which is why cannons have a muzzle swell--to give them more material for strength. With a larger caliber (62 vs. 32 for instance) the arc of the bore is more gentle, and the thin area is thinner longer, which means that you will need more metal between the dovetail and the bore to achieve the same safety factor.
Destructive testing certainly COULD be useful, but I think because of the homogeneous nature of today's steel that we could probably be close enough if we went with the formulas and calculations.
For instance as a purely speculative hypothetical (meaning I have no numbers to back up what I am saying); after being subjected to the shock load firing of 1000 rounds, and a pressure of 8000 PSI for .008 milliseconds, with a curve of 3F's burn rate, the elongation factor of hot rolled 12L14 with an unsupported thickness of .10 will be reduced to 18, and the brittleness has increased to 12. After another 20,000 rounds the elongation would be reduced to 6, which reduces your safety factor to .2, and after which a catastrophic failure could be expected within the next 1000 rounds.
We could then calculate / infer the failure points of other thicknesses, without having to go to all the trouble of many many thousands of rounds to get to the catastrophic failure point.
As an analogy, in commercial aircraft, the number of "cycles" on the pressurization of the cabin is kept track of, and, after a certain number of them (say 20,000 or so) the brittleness of the aluminum will have increased to the point where failure can happen. Remember that Aloha Airlines 737 that turned in to a convertible about 30 years ago? That's an example of metal fatigue, or increased brittleness that was unfortunately, tragic.
Somebody like MD or Zonie please chime in here.