Reamers that have been sharpened can be under spec in body dimensions, but the bolt will still close on a go gauge and give a false positive, because go gauges only spec headspace. If factory ammo won't chamber in a SAAMI chamber there's an obvious issue with the chamber or the ammo.
Harvey_NW,
I think we are saying the same thing. The reamer and go/no go guages are ground based on the SAAMI drawing with exceptions to custom modifications IE: the AW II reamer, and others.
I agree that a re-sharpened reamer could certainly cut an undersize chamber, the fact that the chamber is undersize is a departure, albeit a very small departure away from the SAAMI spec.
I suspect that there might be a number of variables in play here:
-As you mentioned, resharpening...Reamer tolerances small.
-Go/no go gauges that are out of tolerance.
-Machinists that aren't performing their finest work, or doing their finest dimensional inspection.
-Tooling inspections, particularly reamer inspections with a CMM.
I can tell by your response that you know your way around machine tools thus, I also can tell that you know there are many other variables that could contribute to rifles failing to chamber.
If the tooling is correct and the chamber is machined per print, indicated properly, correct feeds and speeds..... ..Ammunition, (especially Factory) is not the likely culprit.