Ok - since folks want a metaphor, I will give a similar, but better metaphor. A circuit breaker is designed to trip at a certain amperage. Sometimes a weak breaker when you are getting close to this limit it will buzz before popping (or not pop, but i cant think of a better analogy). Let us assume for this discussion the buzz is a warning and not faulty. I gather you are looking at brass like it tells you this limit. Since there is no similar limit for brass, this idea is flawed but let's assume it is ok
So, you are looking for the buzz. If you don't like where this buzz is happening you get a higher rated breaker (stronger brass). So in the case of your handload you are running at higher pressure and feel ok about it because backed off from the buzz.
So what does this mean? If you look at a # of cycles (shots) vs stress (pressure) curve for steel (action) , the # of cycles before failure decreases exponentially with the increase in stress. So, running an action at normal pressures may give you 10's or 100 thousands or more rounds, running at higher pressure can quickly reduce to few thousand rounds before strain lets go even at standard pressures. This is also why proof loads are only shot once. Single high pressure events can significantly decrease the life of an action to point where "normal" pressure loads cause failure. I am under the impression from folks on this thread that just because an action can survive a single event at much higher than normal operating pressure (ie 100k) that means the system is overly conservative. That are certainly safety margins built in, but it is not as black/white as made out to be. Like I said, folks who dabble outside the system need to understand these things and that is not best place for a novice
Lou