Question first : If you are in China, truly in China, you also know it's also illegal for you to own a gun at all as a private citizen. Only military, police, Secret police, etc. carry or have guns. Or, you are looking for ideas to make your own. China .... the last I knew, doesn't allow importing them either.
And having or smuggling one in, has some very very severe penalties.
If I'm wrong ... educate me, but I doubt it's changed since I was working there.