I have several uppers. In the 1:9 I've never gotten it to shoot anything but 52gr match bullets well, and those with 26.5gr 748 in a WW case with CCI primers. Those it shoots into a little knot at 100 yards, and the same at 200 if there is no wind.
A 1:8 shoots lots of things well, especially 69 grain bullets using 4895. In the 1:8 barrel, Sierra 80's shoot well just off the lands using RL15 and Winchester primers in a Winchester case. I bought a 1:7 barrel a year ago and have not shot it much (waiting for the 1:8 to wear out).
I've never gotten either Hornady 75 to shoot well in anything, but many other people get them to do great things. I've also played some with Berger 80's, but they are very tempermental.
You will find some threads on cast bullets in the AR over on the Cast Boolits board.
CDD