Turkish 8x57mm Ball Ammo.
 

At our last gun show nearby, I did not make it there on Saturday, but I did get there after church on Sunday. The vendors were packing up to leave. One vendor had blue cloth 70-round bandoleers of 8x57mm Ball ammo for $10 each. The ammo was clean and bright and was put up on nice sturdy brass chargers. The vendor had 3 bandoleers left and told me I could have them for $20. I bought them and tested the ammo yesterday. In my Yugo M48A the stuff shoots to point of aim at 100 yards and was sure fire. I have a 5/8" steel gong near the target frame and I shot a clip of ammo at it, hitting it all 5 times. When I walked to the target frame, I glanced at the gong and saw all rounds went through it! Ok, if that is BALL ammo, I wonder what Turkish armor piercing 8mm ammo will do. If the new Congress allows future gun shows, I will get a few more bandoleers of this Turkish ammo next Summer.

Adam

I've had goo dluck with the turk "ball" ammo as well, but i do believe there is some of it that is steelcore, which may be what you got.

Easy way to find out is the good old magnet test, if the bullet sticks to it, it's steelcore.