Finally, something I know about on these forums! The powders mentioned work well. I would also like to offer up Accurate arms 2460 for bullet weights up to 69 grains and Acurrate Arms 2520 for bullets up to 80 grain. It is a ball powder and meters extremely consistently in any powder drop. They are very clean powders and give excelent accuracy and velocity for the .223. Also it is usually easier to find than some of the other brands. For that bullet I would look at around 24-24.5, but start low and work up! Out of my 20" barrels I get around 2950 f.p.s. with a 69 SMK. I am an avid 3-gunner and have been since 1995 and my match load is a 55 gr. BlitzKing/Ballistic tip with 25 grains of AA2460. I have conservativly burn up over 80 pounds of this powder in that time. Try it you will like it!