I have a load using the 75 grain Hornady HPBT bullet using IMR 4064 powder and CCI BR4 primers. However, IMR 4064 is both rare and expensive. Accurate brand powders are more available, but I have no experience with them. What AA# powders are intended or known to work well with 69 - 77 grain bullets? I'm also looking into Shooters World powders and use AR Plus and Tactical Rifle in both 308 Winchester and 223/5.56. For what it's worth, I very rarely load bullets to full 5.56 pressures.