Hodgdon website: 223 Rem, H335, 25.3 GR. 55 GR. SPR SP, 2.200", 24" barrel, 3203 fps, 49,300 CUP
Test 8-19-2003: Ruger #1, CCI 400 small rifle primers, LC brass once fired processed from Scharch and prepped by me, 55 gr Vmax moly, H335
pic left to right: unfired 27 gr, 28, 29, 30, and 31 gr.
27 gr, unfired, extractor groove .329"
28 gr, extractor groove .329", 11% overload 69 kpsi QL estimate
29 gr, extractor groove .329", 15% overload 80kpsi QL estimate
30 gr, extractor groove .3295", 19% overload 92kpsi QL estimate
31 gr, extractor groove .3320", 23% overload 106kpsi QL estimate
What does it all mean?
Beginning or otherwise novice reloaders use 25.3 gr.
Advanced reloaders find the threshold of extractor groove growth between 29 and 30 gr, and then subtract 4% margin = ~ 28.3 gr for long brass life.
The advanced answer for any .223 load will ultimately be 75 kpsi in Quickload, if you want to cut to the chase.