Not really. Our worst massacre, and many leading up to it, were all committed with legally obtained weaponry. We used to have killings every now and then, with a few deaths in each one. Now we have none.
Of course, illegal gun crime has gone on largely unaffected. But at least we don't get public places being shot up every 2 years anymore. But extrapolating any of this to the US is a very stupid thing to do. Even when it was easy to get guns, not many people owned them, certainly no where near the ownership levels of the US. So a gun ban and buy back scheme was pretty effective given the small amount of guns spread among the populace. That's not the case in America at all.