Hodgdon has a new one called CFE 223. It's designed almost specifically for 223/5.56, and prevents almost all copper fouling in the barrel. Not sure how they do it, but apparently it works really well.
I haven't been able to get my hands on it as it's selling out about as fast as distributors can get it, but if you can find some, I would definitely try it.
"Breathe when you can, shoot when you should."
"Qui desiderat pacem, bellum praeparat; nemo provocare ne offendere audet quem intelliget superiorem esse pugnaturem"