Probably 60gr. MAYBE 62gr if you pushed it hard.

It's a shame that most factory bolt-action .223 Rem's are barreled with the slow twist only. I see that with a few models Savage is offering the .223 and .22-250 in both a slow and fast twist version. I know a LOT of .223 shooters are moving toward the heavier VLD style bullets to stretch out the .223's range, but if that's what you want to shoot you're left with either a custom barrel or an AR-15.

Mike