My best BL-C(2) load in a 1:9 twist with 52-gr. Sierras is with 28.0 grains. Had much better accuracy with the 28.0-gr. load behind Sierra 53-gr. Match. Had several 5-shot groups in the .200s. Also, I never use magnum primers in the .223, as I find CCI 400s or BR4s are more than sufficient in the little case. Good luck ...