I've said it before and gotten some mild flames, but here it goes again:
[b]Templar's Rule on Surplus Ammo:[/b]
[b]NEVER BUY AMMO FROM A COUNTRY THAT PISSES IN IT'S OWN DRINKING WATER![/B]
Follow that and you won't have any problems.
Stay the hell away from Indian, Pakistani, Chilean, Chinese, and Venezuealan ammo in 7.62x51mm. Also, Israeli surplus TZZ 81 headstamped ammo is bad juju. I still have scars where a civillian Class 3 M60 let go on me while shooting that crap. The Israelis are too poor to surplus anything out unless it's trashed. New Israeli is good stuff.
The Czechs made some corrosive ammo for there revolutionary brothers in the Colonial Wars in Africa in the 60's and 70's. SAMCO Global has some, so be advised it's corrosive.
German, Swedish, Dutch, Austrian, British, Canadian, Australian, South African, Portugese, Spanish, Malaysian, Singaporean, and new Israeli 7.62x51mm is all good stuff.