I was hanging out with the security guards, and one of them is quite the grizzled warrior. He has bullets wounds from both Russians and Taliban.
I was chatting with him about weaponry, and the differences between Chinese/Russian/KyberPassCopies came up. He pulled out his magazine and went through the rounds, and identified them by sight as being from either Russia, China, or Pakistan. The Pakistan ones, in his humble opinion, are crap, with the Russians being the best.
If found this interesting, because there was obvious corrosion on the jackets of the Russian ones. He stated the insides were perfect. I asked how he knew for sure...
At which point he manually extracted the bullet from the jacket and dumped the powder out on a piece of paper so he could examine it. I can't tell you what parameters he was judging... the finer points of inspecting the interior of 7.62x39 rounds escape me... by the time the bullets leaving the jacket I prefer to be far, far away.