Like Norseman said, just run all the brass through a .223 sizing die, and regardless of what the headstamp says, they're now sized to .223 chambers. Trim as necessary after sizing. I separated mine at first, but only because I wanted to maintain similar headstamps for load development/sighting in. Once that's done, I probably won't keep them separate.
But as has been said, load all of them as though they are .223 brass. If you load .223 brass to 5.56mm specs, you may seriously regret it.