Sgammo.com. Sorry
I just bought 1K rounds of brass 223 from them about 2 weeks ago. It arrived in a few days. I also found some other stuff using ammoseek.com which is just an ammo search engine as they describe themselves. The price for 223 is up about 8 cents per round in the past 2 weeks. I paid 34 cents per round and it's now about 42/43 cents.
SGAmmo is a family owned business, great service, reasonable shipping, never been disappointed.
If they don’t have ammo, it’s really dry.
Where I work only gets ammo in small batches lately and its gone as soon as it gets put out.
We usually have pallets on hand.
Weirdly, unlike last time, rimfire still seems plentiful.