"There's effectively a permanent amnesty," police deputy commissioner Mike Clement said.
"If, in the right circumstances, you were to bring a firearm in, then we would treat it as that and there wouldn't be a prosecution."
He said he has been in close talks with his Australian counterparts about how their buy back process ran after the Port Arthur massacre in 1996.
After the initial wave of buy-back events there, the amnesty was extended and the police ran dedicated collection events in the following years.
"That would certainly be our approach as well," Clement said.
"There's already provision in the Arms Act and it's intended that will continue that there's an amnesty in place, but you just won't get money for your firearms that are illegal or you don't need any longer.
"It's something that we are absolutely turning our minds to."
Heading into the final month of the buy back, 22,000 people have handed in 38,000 guns and more than 140,000 parts.
The government has paid out more than $73 million as a result.
Nicole McKee from the Council of Licenced Firearms Owners said an extension of the amnesty is good news.
But she said the council estimates there were 200,000 prohibited firearms in circulation, and the government needs to extend the buy-back in order to get them all handed in.
"We are going to be well short, and that means that this event has become a failure, and I don't think it needs to be," McKee said.
"From our perspective, it's really important that prohibited firearms are handed in, but if they're not being handed in then we have to look at how we get them handed in.
"Threatening people with sending them to jail is obviously not working.
"What we're seeing is a number of really fair minded, law abiding people, jacking up because they don't like the way they're being treated."
McKee said if their numbers prove true and more than 100,000 firearms are not handed in as part of the buy-back, she feared those guns will fuel the black market.
Clement admitted the police still don't have an idea of how many prohibited guns there are in the country.
"It might sound defensive, it might sound easy for me to say, but the reality is I can't be precise and no one can about what the number is," Clement said.
"All I can do is make sure we're engaging with stakeholders and importantly the gun owners, and providing confidence to them that we've created the opportunity for them to bring their firearms that are now prohibited forward."
Clement said he expects a late flood of hand-ins.
"A couple of my own colleagues have said that to me, 'oh there's plenty of time, we've still got another month'.
"You know, we'll be open, we'll stay open on the 20th as long as it takes, but the reality is, why would you want to be in a queue that snakes out the door immediately prior to Christmas?
"And also, the sooner you get in, the more likelihood you're going to get the money prior to Christmas."
An updated list of upcoming firearms collection events can be found on the police website.
The last day to receive compensation for the guns is 20 December.
