Also, never reload 5.56 casings to .223 reload specs. The cases are thicker, and if it is filled with a powder charge according to the .223 load specs, it will have higher pressure due to the decrease capacity of the 5.56 shell due to its increased wall thickness.
Most powder manufactures advise to back of 10% when reloading 5.56 to the .223 loads, but why take the chance. .223 brass is cheap, just make sure you are getting .223 brass not once fired military brass.