I load the .223, however, I do not use 748. What I have discovered is that the best load for .223 is the load your rifle likes. I recommend first finding a powder charge that has acceptible accuracy and velocity without being over max. pressure. Then alter the seating depth using that charge to find the best combination. Every barrel is different. Also, try not to deviate from the exact powder/primer/case/bullet combination from the load book. Big changes in pressure can arise from substituting components, even primers and cases.
