Firearm advocates are threatening court action if they're unhappy with the buyback scheme.
Details of the scheme are set to be announced on Thursday, and Newshub understands gun owners will not be paid full retail price for their firearms.
Instead, owners will get more if the guns are near-new and less if they're in poor condition. The top price offered for each weapon won't be its full retail value.
Council of Licensed Firearm Owners spokesperson Nicole McKee hopes that's not the case.
"The Government has, multiple times, said to us that they're going to make sure this is done properly," she told Newshub.
Newshub understands police will hold 'collection events' in large community centres - for example, in small towns they could set up in town halls or rugby clubs, while in larger towns it could be stadiums or even racecourses.
- Police haven't ruled out buying back guns stolen from them
- What Government's gun buyback scheme will and won't cover
- How the Government will work out how much to pay for guns
McKee says the compensation process needs to be easily accessible - and owners should be able to drop off firearms at police stations or have home collections.
"I think there needs to be a lot of emphasis on the fact this is not just about semi-autos or MSSAs - it actually affects a huge range of firearms."
She's also heard rumours "not all parts, accessories and consumables will be considered as part of the compensation, yet they will still be confiscated".
The full details of the $150 million buyback scheme, implemented in the wake of the Christchurch atrocity in March, will be will be revealed at 10:30am.
"I think we've struck a fair balance - I really do," Police Minister Stuart Nash told Newshub.
"We've come up with a comprehensive plan to ensure that people, I think, are fairly compensated. I think we've struck a really good balance."