As far as I know, all of them - USSR, Cuba, China, Vietnam, NK etc, implement gun control. Why should their governments do that? The people of these states genuinely support(ed) socialism, if they are/were all armed they can protect socialism far better than the 1% of the population that makes up the military.
why the socialist states didnt allow arms is an obvious thing, it's becuase revolution is bad when it's against you. how a future socialist state would be forced by the working class to not ban arms is another story which is harder to answer