Its really hard to go wrong with the FFII 3-9x40 with ballistic plex reticle. You could also go with a Burris MSR in 3-9x40 or 4.5-14x42. That is what I run on my 223 bolt gun:
The nice thing about the MSR is you can order a custom dial for the load your are shooting. It also has the ballistic plex reticle, but more calibrated for the 223 cartridge.