Hi, Boomer,
Sorry about the late reply, I didn't see this conversation till now. Maybe you can refresh my memory on this, thread ID..?
In general, I think 1.632" is minimum, I like a tad longet just because I am not a match shooter, but I want reliability over anything else. Which is why the NATO chamber min is 1.6355". Bear in mind that all ammo is the same dimension, (NATO vs commercial) but note that NATO MAX dimwnsion for the case is 1.6319" (from 41.45mm). So it is POSSIBLE that you can gat a NATO case that actually is right at your chamber HS which is not good. ANY crud or other stuff in your chamber can then cause ejection issues and possibly affect reliability. So IMO, 1.634" is about right for both NATO and commercial.
Of course, Fulton Armory disagrees, but such is life. We all have our reasons for doing the things we do.
JWB