The case of Australia (facts from an interview):
"....But, basically, the laws became pretty much uniform across the country. And as part — as you mentioned earlier, as part of that, the ban on semiautomatics, those guns were bought back, so they’re no longer in circulation. And because the law changed at the same time, those — like, sometimes there are buybacks, but the law doesn’t change, so it’s kind of like just mopping the floor while the tap is still on. If you change the law at the same time, then those guns cannot be immediately replaced with similar weapons.
And really, the result has been a spectacular success. We didn’t have another mass shooting incident for almost 25 years. And we just generally have much lower rates of gun violence, and also a lower rate of fear. You know, we don’t think at all about the possibility of being murdered as we go about our daily lives in Australia."
“Enough Was Enough”: How Australia Reformed Its Gun Laws & Ended Mass Shootings After 1996 Massacre | Democracy Now!