Given the relatively recent example of Britain, Australia and Canada, it appears that restrictions on the owning of firearms by law-abiding citizens (and quite obviously the criminals just ignore gun laws.... in any country) doesn't reduce violent crime. In fact, these examples show an opposite trend. I believe most would say these three societies are a bit more similar to that of the US than either Japan or Finland.
It will be interesting to watch the statistics over the next five years and see what happens to the trend.