I read somewhere that at one point, Japan had more firearms per capita than any other nation on Earth, and Japanese gunsmiths produced a variety of high quality arms. However, the ruling samurai class was eventually able to heavily restrict their manufacture and ownership, and a gun culture never emerged in Japan.
What if instead of restricting firearms, the samurai class had incorporated them into their existing style of fighting, only prohibiting them for non-samurai? Alternatively, what if the samurai had been unable to stop the technology from proliferating, and firearms became commonplace?