The 223 is a very easy cartridge to load.
Full size completely for that AR.
I suggest anything from a 55gr to 69gr bullet to start (assuming 1-9 twist)
Go with IMR4895 powder for now. It's the do-all Chevrolet of propellants.
Use CCI small rifle primers -- NOT
Federal as they are too soft for the AR.
Pick a powder charge about halfway (or lower) from min-to-max for whichever bullet you choose.
Seat to the recommended OAL in the Speer book for that
Back the seating die off contact with the case mouth a half turn before locking down (i.e., no crimp).
Adjust the seating stem to the specified OAL after that.
Relax and read the Speer manual in the bathroom as necessary. It's one of the 3 best manuals.