.223 with Benchmark
You didn't state the type of rifle (Bolt action vs semi-auto) or barrel twist rate - these factors will influence your powder loads.
My rifle (a Cooper .223 bolt action, 1 in 14 twist 24" barrel) performs superbly with 24.5 to 25.5 grains of Benchmark, using the Sierra 52 grain Match Kings, as well as the Sierra 50 grain Blitz Kings. I know of others who use similar loads with good results in a Savage 12BVSS (1 in 9 twist barrel).
Velocities are in the 3150-3300 fps range.
I seat the bullets .015" off the lands, although that seating depth will result in a longer C.O.A.L. than listed in the reloading manuals.
The cases I have used so far are Black Hills Match headstamp (reloaded from once-fired factory ammo). I don't know who manufactures the Black Hills cases. My primers are CCI BR4.
As usual, it is advisable to start with lighter powder loads and work up, always looking for signs of excess pressure.