Re: .223 vs. 5.56 breakdown
The .223 Rem is SAAMI registered at 55 kpsi, but gets long brass life at 75 kpsi.
Compare that to the 270 that is SAAMI registered at 65 kpsi, and can get long brass life at 67 kpsi.
Or the 308 registered at 62 kpsi and can run 67 kpsi [same case head as the 270].
Then there is the incalculable error of strain gauges with calibration ammo [no trace to NIST].
What does it all mean?
A person could get distracted from what is important or never figure out what is important.