I gave the 168 grains a try today. Loaded some to 30/30 published COL, and others almost to the rifling. Like Jeff's loads, the longer ones were terrible, looked like I used buck shot. The 30/30 length was better, but still not real groups. I was using IMR 4064, and loaded on the light side. I'll try a heavier load, and if that don't work, I'll switch to Varget and see how that does.
The good news is I was able to get my best group ever out of my .223 Ultra. It shot a .43" five shot group at 100 yards, unfortunately I was using the Winchester USA 45 gr. JHP ammo and not my handloads. It seems like the different things I've done to that rifle, have combined to make it shoot better. Switching to the Bushnel 6-18x50, weighting the stock, trigger honed and action polished, and of course the old o-ring.
Don