the 223 Rem and 5.56 have different pressure limits. I have always loaded to the pressure limits of the 5.56 without any issures.
Difference in barrels(#of grooves, bore dia, Groove dia) lot# of powder, lot# of Primers, differnce in chamber configurations all leade up to a conclusion that a Reloading manual and Quick Load are for reference only. You will have to use your own best judgment in what is safe in your rifle.
