Police are hitting back at claims the gun buyback won't make New Zealand safer, since bad guys won't be the ones handing over their weapons.

The first weekend of the buyback scheme went by without a hitch, firearms owners in Christchurch handing in more than 500 now-illegal weapons, and receiving more than $1 million in compensation.

"We've put an awful lot of effort into getting ready for the weekend and that worked very well," Deputy Police Commissioner Mike Clement told The AM Show on Monday.

"We've got some things around the edges to tidy up, but I thought that went extremely well."

The buyback was implemented after the Christchurch terror attack in March, in which 51 people were gunned down at two mosques - by far New Zealand's worst-ever mass shooting. When a similarly tragic rampage took place in Australia in the 1990s, more than 660,000 guns were surrendered in the resulting buyback.

No one really knows how many now-prohibited firearms are out there in New Zealand at present. The Government has allocated a couple of hundred million dollars to get them off the streets, and is prepared to spend more if that's what it takes.

But the buyback process has come under criticism from ACT leader David Seymour, who told Newshub at the weekend it wouldn't make New Zealanders any safer.

"People who are prepared to line up in the full public glare and hand in their firearms at below-market rates are not the people we should be worried about," he told Newshub.

His view is backed up by Australian homicide researcher Samara McPhedran. She told Magic Talk in June that gun buyback schemes don't really achieve what officials think they will.

"Based on the Australian experience and international evidence, there is very little evidence to suggest the path New Zealand is taking, and the path that Australia took in the 1990s, has any real impact on public health and safety," she said.

"That the people that tend to hand in guns aren't the high risk people who tend to be involved with firearm violence."

But Clement said it doesn't matter who owns the guns now - as long as they exist, they're a threat.

"I can tell you that there are far too many guns that are evil in their nature in this country... The vast majority of firearms in the hands of criminals are diverted from the legitimate fleet - in other words, they are stolen in burglaries.

"I'm not blaming gun owners for that - they have security, we have more determined criminals who are prepared to break in... and steal those guns. That's the vast majority of guns that we find in the hands of criminals."