Tonight marks the end of the gun buy back and amnesty, with thousands of guns handed over to police.
However, the Council of Licenced Firearms Owners say owners have been "hiding valuable firearms, protecting family heirlooms, and being ignorant of the fact they are affected by the new bans is now the new normal".
The council estimated that 100,000 unlawful guns won't be handed back after the buy back ends tonight, a figure it says came from talking to 11 of the 15 large gun suppliers and from custom numbers.
More than 56,346 firearms have been handed in so far after the law change was spurred by the March 15 Christchurch terrorist attack, in which 51 people were killed.
KPMG, who independently estimated the price of the buy back for the Government, estimated there could be 56,000 to 170,000 that fell under the newly banned firearm category.
In its June pricing report, it pointed out that "in building estimate of the potential cost of the buy-back, the majority of data sources have lacked rigour and have been riddled with assumptions".
"One of the challenges in determining the overall cost of the buy-back is a lack of data relating to the actual firearms that are in public ownership."
It also said data provided by a major gun retailer was "limited" as it only covered a sample of firearms on the base price list.
"These estimates should also be used with caution because the volume data provided was comparative rather than based on actual sales information."
Police Minister Stuart Nash said there had been a last minute surge of people bringing the prohibited and unlawful firearms.
He said 56,000 firearms had been bought in and about 32,000 people had taken part in the buy back, with almost $100 million paid in compensation.
"There has also been a huge number of prohibited parts handed in, such as high-capacity magazines and pistol grips, which can modify existing firearms," he said. "Almost 188,000 prohibited parts are no longer in the community."
“Another 1800 firearms have been seized from gangs and other offenders since March.
"From tomorrow gun owners will not be paid for their prohibited firearms. The buyback will be over. Those in breach of the law face risk of prosecution and up to five years jail, as well as the loss of their licence."
National, who voted in favour of the first phase of the gun law reform, called the buy back a "failure and the blame for that is squarely on the Government".
"It’s clear why only a small number of firearms have been handed back and it’s on the Government that rushed the process, wasn’t clear on requirements, changed the prohibited list during the programme and failed to engage with the firearms community," justice spokesperson Mark Mitchell said.
"The result is a lot of confusion and lack of engagement."
ACT's David Seymour, who has been against the law changes due to the speed, today told media today: “The truth is that we had a law-abiding firearm community who, in my view, have become engaged in civil disobedience on a massive scale because Parliament eroded the respect for the law when it disrespected its own law-making processes.”
Licenced Firearms Owners Council spokesperson Nicole McKee said "from tomorrow, there will be a number of good people who will be made criminals by this Government's arrogance, and this is the new normal".
"Why would they hide them? They're angry, they're angry at the mistreatment that they have received and the blame have received for an event they did not do."
The Prime Minister announced the second tranche of proposed gun laws in July . It included the creation of a gun register, dropping the length of gun licences from 10 years to five and police being given additional powers to put warning flags over people.
1 NEWS was leaked a draft version of the legislation in August.
The registry would work in a similar way to vehicle registration, holding the name of the owner, date of birth and address, as well as the firearms licence number. It would be available online and include a paper-based option.
Mr Nash said that police had "consistently warned the problem is we just don’t know exactly how many guns are out in the community, this is why we need a register, to enable Police to better track firearms".