Quote:
mehavey
Take it from me. When you exceed 55K (per QuickLoad cals) w/ 223 by any substantive amount, you start opening up primer pockets to the point that 5-6 firings and you're done.
Not so much catastrophic failure and/or brass extrusion into ejector cutout on any particular shot-- the brass just can't handle the cumulative effects over multiple shots.
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I did a study of different 223 dies for case length growth and concentricity over many firings and lots of pieces of brass. My standard test load was 66k psi Quickload, because that was all the powder that would fit. Brass went 25 firings and never got loose primers. Lengthwise case growth with FL sizing is faster with higher pressures.
When I work up to find changes in the extractor groove, which is a very sensitive pre cursor to primer pocket growth, the threshold in 223 is between 80k and 92 kpsi Quickload.
This is in contrast with 270 that is SAAMI registered at 65kpsi and I cannot get above 67kpsi with margins to stay away from primer pocket growth.
Again, the magnitude of the margin between SAAMI registration and case head capability is something like 3% in 270 and over 30% in .223.
The future may bring us commercial 223 +P and/or 223 +P+.
The future is not going to bring us any commercial 270 +P. Not with H06 tempered C26000 brass and large Boxer primer pockets in 270 and .409" extractor grooves.