My only .223 is a heavy barrel Savage 112-V. After considerable experimentation, I have found the best load for it is 21.5 grains of IMR 4198 and 50 grain Remington bullets, 5-shot groups at 100 yards are typically 1/2" or less. The case headstamp does not seem to matter. I neck size only, but I do trim them to length when needed. Don't forget that the bullet seating depth will have a significant effct upon grouping performance, so you must experiment with that also.