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.
NRA Life Member, SAF Member