Feed a .223 imr 8208 xbr and don't look back. If you want more accuracy, 6mm br or 6.5 grendel, no need to go back in time to a .222. I played with.222, ai, 222 mag, ai. They are good cartridges in their own right. But not more inherently accurate than many others out there. .223 with 8208 xbr will give 3/8" or better in most "good" rifles and much smaller with a "great" rifle.