“And if too small(the chambers headspace) wouldn't there be indications of excessive pressure? “
Yes, the case should stretch to fit the chamber, no, not if the smith cut the chamber to Min specs. Meaning no room to stretch, a good thing.
Will a small chamber have an affect on pressure, no not if it is in the chamber, yes, if it is in the throat.
Not an easy concept to grasp, Unclenick takes the time to introduces reloaders to sequences of events that happen after the trigger is pulled, instead of thousandths of an inch time is used as in milliseconds.
And I say time is a factor, as time applies to Jason’s question, a case that does not fill the chamber must expand before pressure builds, if the case fits, is formed and fills the chamber before firing time is not wasted on case expansion. I formed cases for a wildcat, I used a heavy bullet and too much powder, friends informed me “that is some risky stuff”, the bullet and powder combination was the maximum load for that chamber after the cases were formed, but because of the case expansion when forming the bullet was out of the case and traveling down the barrel before pressure was high enough to cause concern, as opposed to the same load after forming the cases, the form case does not expand to the chamber, time is reduced, pressure climbs before the bullet gets started down the barrel. My fire forming load was the maximum load with formed cases. The shoulder of the formed cases was formed .202 ahead of the parent case, the diameter of the case body was increased and the shoulder angle went from 17 degree 30 minutes to 27 Degree. And I was told I was forgiven for a big mistake.
So, yes, the size of the chamber does effect pressure, when keeping up with many factors at the same time “wouldn't there be indications of excessive pressure” I would say an increase in pressure when the case and chamber has little room for air room between the case and chamber, not necessary excessive high pressure, but time is a factor, reducing room for air between the case and chamber increases pressure.
I am the fan of cutting down on all that case travel, I want my case to fit the chamber from the bolt face to the shoulder, I do not insist the case body fill the chamber.