Re: 7.62x51 308
Yup, I've been preaching that gospel for more than a decade now.
Ran QuickLOAD on some .308 loads that were published in the 1980s with CUP pressures, known to be safe with M14 gas systems, and they correlate quite nicely with the general idea that 52KSI CUP is about 60,190 KPSI Piezo CIP. I can't find it now, but the article that even had M14 port pressures (highest with 45.5 748 and 150-gr SMKs and LOWEST with the 190s, BTW) shows an almost even 2,000 PSI difference between old CUP and new CIP Piezo at the 12,500 PSI, +/- 2,000 port pressure standard for that rifle, at 12.5 inches bullet travel to reach the gas port.
Shorter case life, yes. Pressure incompatibility, no.
But I still haven't ever seen ammo dimension specs with minimum AND maximum tolerances for either cartridge.
As far as the chamber dimension differences, I won't discuss them with anyone who has not pulled out a dial caliper and LOOKED at the "difference" dimensions of .005 and .0065 and possibly .0075.