Do not give a flying fuck about Russia which has not been a democracy for a long time.
I want to compare like to like. Western, first world democracies with more or less rule of law. Per the UN's global study on homicide (2019 edition, latest that was released) - the United states recorded 4.96 murders per 100K people vs. 1.2 per 100K in the UK and 0.89 per in Australia.
Also, the UK and Australia never had the abundance of firearms per capita that the US has even before their gun ban. They just never let the problem get so far out of hand as the US has, their gun ban mostly solved the issue of mass shooting. For the record, Australia still has more guns today than it did before the ban, the difference is that it is harder to get one and the percentage of households that have them is much lower (almost a half).
There is no clean cut solution for anything, but limiting access to qualified people (which is what their gun ban really did) - sure did help and it would be absurd to think it would not here. As I said, it is also does not need to be done via gun restriction, but by putting ammunition restriction, so the amount of guns that are already out there is not the huge problem in restriction, once you restrict the consumable resource - you can quickly reduce the problem even with millions of guns out there.