If it's steel cased make sure it specifically says it's non-corrosive. There have been reports of people claiming certain steel cased lots are non-corrosive when they aren't. The Nornico stuff says it on the box and all the reports I've read say it's true.
Anything brass cased is almost always non-corrosive but now we're talking much higher prices. Usually $.75/round or so. The brass is reloadable but that isn't normally a concern for 7.62x39.
The Tulammo stuff is also non-corrosive but is pricey. After taxes and shipping you're looking at $.50/round. It does come in soft point though for hunting if you want to use it for that.