Minimum COAL-How short is too short?

[IDescribe]

Even my shorter than average ShadowLine chamber will handle Berry's RN at longer OALs than what the magazine will accept.

The most likely case here is that there is something wrong with the testing process.

I don't use Blue Bullets, so I can't speak to them.... But all my CZ chambers will load the Berry 115/124gr RN at lengths exceeding the SAAMI Max OAL of 1.169". They typically test in a range between 1.180 to 1.210".

Something is simply not adding up here.

Exactly.  To my memory -- The lighter Berry's RN were over 1.2, and the 147 Berry RN was around 1.9.

[IDescribe]

It sounds like you reload.  If so, you may want to try to incrementally seat a bullet into the case deeper and deeper till it plunks (start at a too long oal).  I'd seat it in 0.005 inch increments till it passes the plunk test.

This dummy cartridge should have been sized, flared, seated, and crimped (flair removed) just as you would during normal loading but no powder or primer.

YES.  For me, I found that between the bullet sometimes sticking to the rifling for a moment and pulling out slightly as I removed it was producing imprecise results.  I also found that unsized brass would sometimes drag and make me think it was the bullet touching the rifling instead of the case touching the chamber walls.  I ultimately just started resizing brass and seating a tiny bit deeper, a tiny bit deeper, a tiny bit deeper.  There would hit a point where it would spin with a little drag against the rifling, then a reduction later, it would spin with no drag.  I found this method to be much more precise and repeatable.