I bought some 7.62x39 and I'm not sure what it is. It came 200 rounds in a sealed green battlepack, packed in 20 round unmarked grey cardboard boxes. Ammo is brass cased and headstamped simply "76 7.62x39."
Yeah ,I really like this mystery ammo too. I bought it for $20 a battlepack at Knob Creek and my only regret is that I didn't buy more. While it's probably too old to count on as SHTF ammo, it seems to be damn good practice stuff.