Owners of newly outlawed firearms have just over two months left to hand their guns in, or modify them.
There have been calls for the 20 December deadline to be extended, but Police Minister Stuart Nash says that won't be happening.
Gun law changes in the wake of the Christchurch mosque attacks mean high calibre semi-automatic rifles, small calibre semi-automatics with magazines of more than 10 rounds and shotguns that can take more than five cartridges are illegal.
Many can become legal if they're modified by a police-approved gunsmith.
Invercargill's Greg Hudson is one of them and told Morning Report he's been exceptionally busy.
"The original consultation with us, as a group of gunsmiths, suggested nine months minimum, and we've been given a bit over 60 days," he said.
"It's a pretty imposing deadline for us and I don't know if it's achievable."
He said the majority of the guns being brought to him are old, often family heirloom, .22 rifles.
"Some of these were manufactured in the late-1800s."
He said the guns were captured under the guidelines as being military-style assault rifles because of the size of rounds.
"The reality is, they're far from that ... it's added a great deal of work where, really, it's probably pretty unnecessary."
"We're talking about the least effective firearms for use by a criminal or terrorist."
Mr Hudson said because the guns are unique and often old, he has to do them each individually which makes it a time-consuming task.