If you look around you can find everything you need for 5.56/.223.
I have a "OK" supply of primers and powder but, should get more bullets.
I have been shopping around and I can still find primers, powder, bullets but, brass is a bit harder to find. I have a few thousand pieces of brass so that's not a big deal.
You may not be able to find "THE" powder that you want but, there are other small rifle caliber powders out there that work fine in 5.56.