The "how close is the brass to my chamber" is only valid for the first firing and for factory loads. You shouldn't chamber to factory loads because there's a tolerance in the SAAMI spec. One brand might fit, the next will be it's own "No Go" gauge.
My 6mm wildcat is based on this very principle. ...And the fact that some companies still 'draw outside the lines'.
Remington factory ammo that I have measured has all been substantially under SAAMI
minimum dimensions for .243 Win.
When my barrel was chambered, it was chambered with a minimum-spec .243 Win reamer so that Remington ammo would
just chamber without binding. A "GO" gauge will stop the bolt, hard, and not allow the bolt to go fully into battery.
So, that rifle is intended for handloads built around the sub-SAAMI dimensions, but I can fire Remington factory ammo in a pinch (or if I want to retest something with my 'baseline' ... which also happens to be Remington factory ammo).
Handloads show zero to 0.001" expansion in the body after firing, except in the SAAMI-spec neck. Remington factory ammo, on the other hand, will show two to three thousandths expansion at the same locations (still far below measured expansion in factory .243 chambers).
But this rifle was a special case. And, even knowing the score... it still gives me trouble sometimes.
For the average rifle, I'd rather have headspace a little longer than minimum. It gives me room to size my brass back into spec with standard sizing dies if it 'grows' a bit too much with repeated use. But with chambers that are super-tight or on the short side, one is generally looking at custom dies or modifying standard dies, in order to get the cases back into tolerance for that chamber.