Well, I have a 223 that has been sat in the gun safe since my CZ527 204 Varmint arrived 18 months ago.
Zipping 39gr Blitzkings at 3,800fps. I drop crows out to 400 yards on a regular basis, the furthest so far being 580 yards. Fast, explosive, great BC and whallops foxes, too.
I chest shot a fox at 230 yards a few months back and it reacted like it'd been hit with a lightning bolt!