My .223 choice is an AR15, w 1 in 9 twist.
I have had a couple, and they all shot sub MOA.
All 55gr ..........PMC, WW, Blackhills (w Hornady SP), and Hornady red tip.
Reportedly, the PMC Bronze FMJ stuff isn't too speedy.
I dunno, my Stag, Bushmaster and Frankengun loved it. So I bought a couple thousand.
Tried the Hornady steel match too, it did fine (but only shot it in the Stag).
The PMC stuff shot very good in my 14" TC Contender. I had a reddot on it and the dot was too big for how well it shot.
Moved the RDS to a .35 rem bbl.