If the lifespan of the patent only lasts for 20 years or so, it seems like a little short given the amount of R&D that goes into a firearm. If it takes a bigger investment then I think the patent holder is entitled to make a profit from it. If it is that easy I would assume there are lot more manufacturers making firearms than it is now.
I'm a little skeptical about Norinco being a defense industry firm from China.
20 years is plenty of time to make money on your design before you move onto the next thing. Also, other companies wanting to copy your design still need to do all the work that goes into making a functional copy (not to mention capital investments on tooling ect), all to build a knock-off of a 20+ year old product.
As for Norinco, Wiki says they employ 276 000 employees, and build everything from firearms to tanks to anti-missile systems. I tried going to their website, but one I don't read chinese, and two Chrome gave me a malware warning every time I clicked on anything, so I'm gonna leave that one alone...


















































