A buyback, which began in July, was intended to allow gun owners to sell their weapons without penalty before the ban took effect. In a statement on Friday, Minister of Police Stuart Nash said that more than 56,000 prohibited firearms had been collected from about 32,000 people through the buyback, a number that was consistent with the authorities’ expectations.
But he added that the police did not know exactly how many guns there were in the country, complicating efforts to precisely gauge the buyback’s success. Mr. Nash called for a national register to allow the police to track firearms. Recent police estimates had put the number of total firearms in the country at about 1.2 million.
The now-banned weapons were collected during public sessions, by police at clubs and gun ranges, and by gun dealers working on behalf of the authorities. In addition to weapons, about 188,000 prohibited parts, like high-capacity magazines, were turned in, Mr. Nash’s statement said.
The authorities paid out almost 100 million New Zealand dollars in compensation (about $66 million in U.S. dollars), but some gun owners felt that the prices offered were too low, according to local news reports.
The country’s largest gun owners group, the Council of Licensed Firearms Owners, called the buyback a “failure” and reiterated its criticism of the new gun-control laws at a news conference this week, calling it “knee-jerk legislation.”
In a television interview earlier this week, Nicole McKee, a spokeswoman, said that the group believed that many more of the banned weapons were not handed in. She blamed “11th-hour changes” to the rules and insufficient public information about them.
On the same television program, Mr. Nash said that he believed that the majority of banned weapons had been handed in. A widely reported estimate by the accounting firm KPMG, calculated on behalf of the government, had put the number of now-illegal weapons at 56,000 to 170,000. But Mr. Nash said he believed the number was not as high as 170,000.
“You would have had to have lived under a rock if you were a gun owner not to understand what the government’s doing,” he said.
The buyback was also affected by a data breach this month, according to local news reports. A German software company, SAP, apologized after details of gun owners’ names, addresses and weapons were made visible to gun dealers. The system was taken offline temporarily while the problem was addressed. Officials stressed that the data was never visible to the general public.
Starting Saturday, those who own banned weapons face the risk of prosecution and jail time, and of losing their firearms license. But gun owners will still be able to voluntarily surrender firearms, with the police retaining discretion of whether to prosecute on a case-by-case basis, Mr. Nash’s statement said.
In making her case for the ban, Ms. Ardern had pointed to Australia’s success implementing gun-control measures after a mass shooting there in 1996. The country implemented strict new laws and carried out a gun buyback that removed more than 20 percent of firearms from circulation. Since then, rates of gun violence and gun suicides have tumbled.
In July, Ms. Ardern announced a second wave of gun-control measures, including a mandatory gun register and a ban on gun purchases by foreign visitors. She argued that the proposed restrictions would have prevented the mosque attacks.
“He would have had to pass a good character test and the register would have alerted the police to the type of gun purchases the terrorist was making,” she said at the time.
The group Gun Control NZ supports the creation of a register, arguing that the laws passed earlier this year are a good first step, but that additional measures are needed.
“The very fact that semi-automatic weapons are now prohibited and the buyback took place is a success,” Hera Cook, a member of the group and a public health researcher, wrote in The Guardian on Thursday.