These days, you have to settle for what you can find when it comes to powder, primers and bullets. Fortunately, there are lots of different powders that work quite well in the .223 Remington. On the minus side, they all seem to be in high demand and don't last long on the shelves. My current favorites are Ramshot TAC, Accurate 2015 and 2200, Hodgdon CFE-223, and IMR-8208XBR. Others I have used and had good luck with are:
Accurate 2230, 2460 and 2520, Hodgdon's H-335, BL-C2, Varget and H-4895, Reloder 15, IMR-4895, 4064, and Winchester 748. Ones I haven't tried but should also work: Alliant Power Pro 1200-R, Varmint, AR-Comp, Power Pro 2000 MR, Ramshot X-Terminator, Hodgdon's H-322, Reloder 7 and Reloder 10. I would try any of these before I used IMR-4198 or H-4198. I just didn't get any decent velocity with the 4198's and accuracy was no better than any of the other powders I have used. Good luck finding some. They are starting to show more frequently in my neighborhood, but are still hard to find in some areas.