My only .223 is a Sako bolt gun.
But, after around 8 or 9,000 rounds thru it and on the second barrel.
I've settled on two loads. Either 23gr AA2200 IF I can get it, or 25gr 4895.
This is for all bullets 55gr and under. I never shoot the heavier one's at all.
The 2200 in my 26" will turn 3100 with the 55's and 3650 with 35 and 40gr.
The 4895 is so close to that it's not worth the hassle to look in the records for the
actual.
Main suggestion I've found is to gather up all the bullet varieties you can find and test them all
with the same load. You'll discover groups from .250" all the way up to 1.5". I'm not kidding.
These loads are safe, but, they are max. So it might be good to cut a grain or two off at the
start to see how your gun reacts to them before jumping into max loads.
Wish you well with it,