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.SAAMI accepted and published reamer and chamber drawings for 300 PRC & 6.5 PRC, June 13, 2018 with zero Revisions. If Fierce were chambering to the stated SAAMI prints, an ammunition mismatch would be unlikely as these issues would have already been considered prior to SAAMI publication.
Dull on size tooling I think would cut oversize or cause chatter.
If the issues are headspace in nature and the go gauge, and reamer are in good shape...the problem is human in nature particularly during the Machinist's inspection and final QC.