Ammo sales were a particular no no.
Private gun ownership was fairly common in the Soviet Union, at about 10 guns per 100 people, and is still common in Russia today. Private citizens were limited to long guns (rifles and shotguns), and they had to register them. But they were generally available to almost anyone that wanted one. The idea that all dictatorships ban private weapons, or conversely, that an armed citizenry always prevents tyranny, is clearly false.