There are concerns modifications to guns to comply with new firearms laws could be easily reversed.
Police are looking into whether kits designed to modify AR-15s from semi-automatic to pump-action would allow owners to keep the rifles, which are used in about half of all mass shootings in the US.
Gun Control NZ co-founder Nik Green says allowing the modification kit would render the new laws pointless.
"Any conversion isn't permanent, so you could quite easily switch it back to being a semi-automatic... It doesn't take these dangerous guns off the streets."
A police spokesperson said they are still looking into the feasibility of modifying AR15 semi-automatics.
"The Police Commissioner will publish the manner and standard required for the safe and permanent modification of these and any other firearms.
A process for how modifications can be carried out - and a list of approved gunsmiths to do the modifications - will be published on the police website soon."
Green says people need to take the moral high-ground, with conversion kits not in the "spirit of the law".
"Our preference is people hand in their guns, take the compensation, and buy a new gun - a gun that is fully compliant, a gun that won't be in the grey area of the law and cause problems in the future."
- Jacinda Ardern announces ban on military-style semi-automatic weapons
- Man who labelled Jacinda Ardern a 'tyrant' speaks at gun reform select committee
Council of Licenced Firearm Owners spokesperson Nicole McKee says the confusion is not fair.
"Firearm owners themselves are out there trying their best to comply with this new legislation, and they do expect to be able to have confidence in the legislators to direct them."
She dismissed claims that modifications to semi-automatic weapons can be reversed.
"Once those firearm parts are handed in... then they can't be converted back, can they?"
McKee says owners are looking to modify because the true value of their weapons isn't being met.
"If they think there is avenue they could take that is not handing in their firearms, but maybe looking at a compensation claim at modifying their firearm, then most definitely hold onto their firearms, for now."
The first buyback event is this weekend.