Without reading your other posts, I see a problem with any test design that tries to infer the pressure of a load for two different guns based solely on the powder charge (and other cartridge parameters) being identical between the two guns. The problem is that the two barrels are almost certainly different. Unless they were made by the same gunsmith with the same tools, one after the other, and installed on the two actions to identical headspace, you may have substantially different pressures with identical cartridges, especially at the high-end pressures that can destroy mauser actions, where things get pretty non-linear.
So, one aproach is to try for two identical barrels.
Another is to put pressure sensing equipment on both barrels and work to calibrate them to similar accuracy, using a chronograph to measure velocities of normal max loads and QuickLOAD to infer pressures from the measured velocities. Then use the calibrations to determine what pressures destroy each gun.
But, way-above-spec pressures from even single rounds can change the actions/chambers/barrels enough to alter presssures in following rounds, so I wonder if the same can be true of the calibrations for the Pressure Trace equipment. At least, the same pressures should be used in each barrel in the same order to tell what difference there is between actions.
After doing all that, you may still have too much uncertainty to reliably call one action stronger than the other, depending on how different the results may be. And, that would be for only THOSE TWO actions, which are no longer available for use. Since they are not new actions and you do not know their complete histories, it is entirely possible that one or both have had undocumented events which partially compromised their strengths. So, to apply the results to any other actions of the same types, you would need to repeat the same test enough times to show that the difference was statistically significant (or not significantly different, if that is your intent). Depending on how different they are, that could be a lot of tests.
If you have a warehouse full of mauser actions, then doing what you are considering might make some sense. But, if you have only a few mauser actions, it seems like you are wasting them for no real benefit.
Anyway, I hope that Clark may chime-in here. He has spent a lot of time testing various firearms to destruction, and probably has a lot of insights that I have tried to avoid obtaining through my own experience.