Reading some of the comments in this thread...
If you want to run heavies, it helps tremendously to have a long throat and a long seating depth. That increases your case capacity for one thing, but more importantly, the long freebore serves to align these high BC bullets so they dont start into the rifling at cockeyed angles.
The picture from grandman here shows a plastic mag, that's another bell ringer for me... These production mags are not made long enough to feed bullets seated long enough to get good performance from a 223 case. If your throat is long enough, you need to modify the mags to feed up to about 2.700" OAL.
The only way I have been able to do it is with the steel AccurateMags or the new MDT steel mags. Both of these can be disassembled so the inserts can be milled to increase the round length. Having done this to several mags at this point, I have encountered no complications from the modification.
BTW, I run a straight 223 case with 26 inch 1:7 twist barrels and with fire formed brass I can maintain 2,900 FPS with 88s and 90s. I do reduce the load to 2,800 FPS for new brass though, just to blow them out. Case life is just fine as I have never yet thrown out a case due to loose primers.
If your throat is not long enough, consider hand reaming the freebore to extend it, or get a smith to do it. You can hand ream accurately if you simply make a bushing to align the reamer in the bolt nose counterbore. Even in an engine lathe, this is advisable to ensure proper alignment.