The bill will outlaw military-style semi-automatic (MSSA) weapons and assault rifles, though there would be exemptions for guns commonly used by farmers for pest control, as well as hunters.
The exemptions would be semi-automatic .22 rifles (with a magazine which holds no more than 10 rounds), as well as semi-automatic or pump action shotguns with internal magazines (holding no more than five rounds).
The Mongrel Mob said at the weekend that it would not hand over MSSAs, but Nash pointed to the new penalty of five years' jail for possession: "My advice to the gangs is, 'Hand your weapons back.'"
Other new offences for using MSSAs or shotguns with more than five rounds include:
• Up to 10 years' jail for resisting arrest
• Up to seven years' jail for use in a public place; presenting them at another person; carrying them with criminal intent; possession while committing an offence that has a maximum penalty of three years or more
• Up to five years' jail for importing, possessing, or supplying or selling, or using a banned part to convert a firearm into an MSSA.
The Government's timeline has been criticised as rushed, with a 14,000-strong petition to Parliament calling for a more thorough process for public consultation.
Nash defended the Government's haste.
"Everyone I have spoken to, be they hunters, farmers et cetera, have said you do not need MSSAs or an assault weapon to go hunting or do farm business. These are guns designed to kill people.
"We don't think we're moving fast in this at all."
Cabinet is still considering the details of the buy-back scheme, which was estimated to cost the Government up to $200 million, but Peters said the funding would come from outside existing department baselines.
"It's going to cost us a penny, but that's what has to be done now," Peters said.
"We're going to have to find either savings somewhere else or increased revenue, but whatever it is, that is not the point. It is to treat people fairly who thought they had a legal entitlement to a weapon that's now going to be outlawed."
The amnesty to the end of September means that people who own guns or gun parts that will be illegal can surrender them to police without fear of prosecution.
Around 200 firearms have already been handed over to police so far, and about 1400 calls have been made to the police 0800 311 311 line.
The bill also bans certain parts that enable weapons to become MSSAs or assault rifles, including bump stocks, free-standing pistol grips and silencers, and magazines holding more than five rounds for a shotgun.
Possessing or selling a banned part could see a jail term up to two years.
The Governor-General through Order in Council will ban types of military ammunition, including possibly armour-piercing ammunition.
A second amendment to the Arms Act will be introduced later this year and go through a full select committee process, Nash said.
For that bill, Cabinet will consider issues including whether a national register of firearms is needed, the vetting process for a "fit and proper" person to obtain a gun licence, and the police inspection and monitoring regime, including rules around storage.
Nash said the gun law changes would be the legacy of those who died in the Christchurch shootings.
"We will tighten gun laws to improve the safety and security of all New Zealanders. Their memory is our responsibility."
What are the new prohibitions?
• Prohibited firearms include semi-automatics and MSSAs; and shotguns with detachable magazines or internal magazines which hold more than five rounds.
• Prohibited magazines include those holding more than 5 cartridges for a shotgun; more than 10 cartridges for a .22 calibre rimfire weapon; and any other magazine capable of holding more than 10 cartridges.
• Prohibited parts include any component of a prohibited firearm, or any component that can enable a firearm to be used as a semi-automatic or fully automatic weapon. Examples could include bump stocks, free-standing pistol grips and silencers.
• Prohibited ammunition will include certain types of military ammunition as defined by the Governor General through Order in Council. Examples could include armour-piercing ammunition.
What semi-automatic firearms will be exempt from the changes?
• Semi-automatic .22 calibre rimfire firearms with a magazine which holds no more than 10 rounds.
• Semi-automatic and pump action shotguns with a non-detachable tubular magazine which holds no more than five rounds.
What about licensed owners who have a professional reason for having a semi-automatic or another prohibited firearm?
• There will be exemptions for specially licensed dealers, bona fide collectors, museum curators and firearms used during dramatic productions, as there are now. They must take steps to disable the weapon and follow other guidelines around security and safety.
• Authorised pest controllers governed by s.100 of the Biosecurity Act may be permitted by Police to own a semi-automatic.
• There are exemptions for Police and Defence Force personnel.
• There is no exemption for international sporting competitions. Further advice is needed and it may be considered as part of the second Arms Amendment Bill which is likely later this year.
How does the amnesty - until September 30 - work?
• Firearms owners who now inadvertently possess a prohibited weapon, magazine, part, or ammunition can hand it over to Police or a licensed dealer without fear of being penalised. Any other firearm, magazine, parts and ammunition not affected by the ban can also be handed over.
• The dedicated Police line is 0800 311 311
How will the buyback work?
Police and the Treasury are working on the details of the buyback, but it will take into account the age and type of weapon, and the market value.
