Thanks. CFJunkie has a long post on his .223 development efforts. He and I also had trouble with the Hornady 68gn HPBT match bullets. But, the Hornady ELD bullets do very well.

For factory stuff, if you can find it, try Black Hills or Federal Gold Medal Match ammo with the Sierra 69gn Matchking bullets (or 77gn if you can find them). They have an excellent reputation for accuracy.

I had bad luck with almost all the less expensive .223 or 5.56 ammo. 1 1/2 to 2" groups were the norm for me.