My plinker load with 55 Gr bullets in .223 is 25.3 Grs TAC. This is safe in even the heavier .223 brass out there, assuming a reasonable OAL. Gives around 2850 to 2900 FPS from a 16" barrel.
Somewhere around there should get you something your rifle likes.
Warning!
This is over some Ramshot 55 Gr bullet data, yet under other Ramshot 55 Gr bullet data. Check the Ramshot data, start low and work up.
I actually liked N-130 in .223 (Had some left over from Benchrest), but my jug went bad. Bummer. Haven't tried N-133 yet. I have a couple of jugs of that left over.