OK, here is my New Zealand story:
Last year, I was at Scottsdale Gun Club when I happened to bump into a guy I had not seen in probably 25 years -- used to shoot with him in the Cactus Combat League. He introduced me to a fellow he said was visiting him from New Zealand. I invited them to shoot as my guests.
This New Zealand guy was a hell of a shot, one of the best I have seen. Precise accuracy, but fast as heck, a way better shot than me, and while I am not a champion, I ain't chopped liver, either.
I invited them to lunch, and we conversed. It became apparent that the two of them attributed all of the world's problems to Jews, blacks, Hispanics, and homosexuals, and the world would be a better place if all of those were...eliminated. Then I noticed an unusual tattoo on the New Zealander's arm. It was triangular, made up of three 7s. I asked him what it was, and he said it was a "brotherhood" he belonged to. After lunch, I looked it up on the internet, and found it is called a triskele, a "three-bladed Swastika." Naïve me, I had been shooting and lunching with a bona fide Nazi/white supremacist, who would like nothing better than to kill me and several members of my close family. (My family is quite "diverse" to use the trendy term.)
Bottom line: I do not see this guy turning in his guns to the New Zealand government. Depending on how many more there are like him, any attempt at confiscation is going to turn violent and bloody. I would not be surprised if the guy I met was acquainted with the psycho who shot up the mosques in New Zealand. Somebody posted that the criminal gangs are not handing their guns in. Well, neither are the Nazi groups. God help the poor cop or soldier who tries to "come and take them."