Actually, IMR4198 is faster than BL-C(2). BL-C(2) is slower than Varget, IMR4895, Winchester 748 and a lot of other powders popular for use with heavier bullets in .223. As Hailstone says, 4198 is actually one of the best accuracy powders with light bullets in .223. It does give up 150 fps off top possible velocities, but it is bulkier than the higher number IMR powders and so it still fills the case well with the 21-22 grain loads you usually end up with. That lighter charge (as opposed to 28 grains maximum for BL-C(2)) cuts down on muzzle blast which helps short range accuracy by reducing bullet base yaw at muzzle exit. It is also easier on the AR gas system, if that's what you have. I like 4198 with the 53 grain flat base Sierra MatchKing, in particular, for 100-200 yards.
I think a good compromise choice for your bullet weights is Reloader 10X, which was developed for light bullets. It will get them into the top velocity range with around 24 grains of powder or so.
Your 9" twist will actually stabilize the stubby 77 grain Sierra MatchKing if you choose to try a heavy bullet. I mention that bullet is stubby because length, not weight, is the most critical thing in determining the twist necessary to stabilize a bullet. A 14" twist will stabilize most 50 grain bullet designs very well, so you actually have more twist than you need for you weight choices, but less than you need for something like the 80 grain long range match bullets.