It's interesting things you discover by testing them yourself.... even with simple inspection.
Since we were discussing the merits of old Chinese steel core, I dug out some 7.62x39 Chinese Cu washed examples that I could easily find. AZgeezer made the comment that not all Cu Washed Chinese ammo was steel core... that some of it had a steel jacket with lead core.
I'll leave sectioning bullets and additional show and tell to someone else...
Bear in mind that Chinese steel core ammo was banned from import in 1994.
I believe at that time all arms and ammunition factories in China were govt owned and operated, so one might assume that all 7.62x39 ammo made before 1994 is steel core, the same as used by their military. It has been said that Norinco was a commercial front for selling milsurp products.
I would expect imports after 1994 to be lead core. I question they would makeup special steel jackets just for that batch of ammo but anything is possible.
When testing these bullets with magnets I first tried a weak business card/refrigerator type- some didn't register anything and others showed a very slight attraction to the case and the bullet.
I switched to a strong magnet from an old disk drive and the attraction was robust to say the least, even at the tip.
The first picture is a group shot showing the Chinese loaded ammo I have on hand. Three of them are copper washed steel cases and look pretty much the same, the Norinco yellow box has black steel cases.
The commercial Blue Box w/head-stamp 351-92 (factory/year) does not have a brand name but says it is made to military specs.
Primers are brass but do not have sealer. I do not see any sealer at the neck/bullet either but there is a very slight groove in the bullet perhaps where sealer would go or a crimp area The bullet tips are strongly magnetic suggesting a steel core (which I believe is the case).
The Norinco Yellow box (black steel case) is marked 71-89 and it too is strongly magnetic. The primers are brass colored and have a red sealant. The bullets have the same slight groove and under a magnifying glass it appears a clear coating has been applied- perhaps lacquer.
Now the interesting part... I have two lots that came out of spam cans.(one I bought and another I split with someone else), both are copper washed steel and look pretty much the same. Both have red primer sealer and a red ring at the neck/bullet. Shown here on the left/right with a side view in the middle.
The first sample is marked 9121-73 and the bullet is a pointed spitzer like the previous bullets above.
On close inspection it has the slight groove in the bullet at the mouth and the red sealer can be seen on both case and bullet as a even ring at the mouth. The bullet is strongly magnetic.
The last example has head-stamp 539-76. Although a spitzer bullet it's point is more blunt and the ogive taper appears different from the 9121 version. Looking at the case mouth shows a definite crimp not seen on the others and the red ring is applied in this area . I don't see the red at the bullet/case juncture so maybe it is hidden inside or maybe the red ring is to make it look like it's sealed. The primer has the red sealer. The bullet IS NOT magnetic at all. This surprised me. This bullet may be a cheap knockoff made to resemble milsurp.
What is interesting is the 76 in the head-stamp, IF it is in fact a date, that is way before the ban, else it must be a code of some sort.
Looking closely at the bullet, it appears to be plated, little dings show how soft it is (indicating lead) but the plating is intact. Again, this bullet IS NOT magnetic at all.
So AZGeezer is correct... some is, some ain't... however in this example, the bullet jacket isn't Cu washed steel, but now I don't doubt there isn't some out there...
ETA....
Just for fun I went out to a Headstamp Codes headstamp collector website and looked up the various codes.... turns out they all are Chinese... Except for one- they have a listing for that odd-ball 539 as being manufactured by Tula in Russian.... That would explain all the subtle differences, so maybe it isn't Chinese lead core after all- I didn't know Russia made Cu washed!
