I think you're missing the point...

most of the rifles cited spent 30-90 minutes being bounced around while in transit to the hunting locale of the day... when the client released the safety in preparation of the shot... BOOM!

we not talking a few months worth of dust here... just a few miles.

No, I assumed that was what you were talking about and I gave what I think are the reasons why it happened or why it happens.

still, I have been told that it can be fixed with some reasonable degree of certainty, but the adjustments would seem (to me) to make the problem worse.

The adjustmesnt are simple, an allen key down through the top of the action for sear enagement and one up through the trigger guard for weight of pull. Actually any of the more recent Wbys come with a very heavy trigger return spring which is alo quite long so that even if you screw the trigger pull weight screw right out of the action you are still left with a heavy trigger return spring tension because the spring is till compressed where it is held captive.

and seriously, who needs a bolt-gun that's that expensive... you're talking $2000+ for most of those guns IIRC... thats a LOT of custom mauser IMO...

Well that is quite a separate issue.

Mike