I couldn' t answer that Clearanceman. The only other thing that I can add is this. The steel bullets that are in the 7.62x39, can be picked up with a magnet (without case, just the bullet) Also, to just look at the bullet, you would swear that it was a normal copper-jacketed bullet. However, you can take 120 grit sandpaper and with just a few swipes, you can wipe the copper right off. It must be anodized onto the steel or something. Not much thicker than paint. I don' t know why it doesn' t come off in the barrel, but I have no signs of copper fouling in the bore.