I know Cheaperthandirt has had some trouble with keeping Tulammo, Silverbear, & Brownbear in stock in the following calibers: 5.56x45, 7.62x39, and 7.62x54R.
I've even noticed shortages in things like .30 Carbine from manufactors like BVAC...
ugh...havent shot the others you mention, but Tula is dirty as hell.