I use Benchmark, 53gr V-max, and either BR4 or CCI450 primers in the three 223 rifles of mine. Two of the rifles are factory Remington SPS Varmint barreled actions, 26” 1:12 twist
The third 223 is a CZ 527 American, 22” 1:12 twist barrel
In the Remingtons I drop 26.9gr of BM resulting in 3560fps-3580fps depending on the rifle.
The CZ I drop 27.3gr of BM and its running around the 3450fps neighborhood.
I really enjoy my 223s!