Oh, if you find any place that has Guatemalan M193 equivalent, it's very clean, also rather hot load, but you really ought to be able to see it in person...I wouldn't buy it over the web. (disclaimer, it has not been fired from a direct-impingement rifle, so I have no idea how well it works in an AR. Saigas will eat anything that goes bang.)
Apparently, some lots got into a hurricane down there, and even the battlepacks were compromised. So some lots will be perfectly sealed and be mirror-bright brass, others will have gotten wet and look like a corroded AA battery.
I just went and poked in the 5.56 chest. Wow, what an international mix. A can of British greentips on their strippers in bandoliers, a few battlepacks and boxes of the aforementioned Guatemalan, and some Israeli even. I haven't seen any surplus coming in lately, though. It seems to all be staying Over There.
What else can you buy now besides Lake City overruns or older lots, all that?