AUSTRALIANS have surrendered 26,000 firearms as part of the national gun amnesty - and they've come in some strange shapes and sizes. Even a hand grenade was handed in.

Police have reported some of the quirkiest guns handed in are among the vintage variety, including a luger pistol from World War I, a Smith and Wesson .455 revolver from WWII and a shotgun from the Vietnam War.

Other disturbing finds include machine guns and a homemade sub-machine gun handed in anonymously in Sydney.

"There's guns that've been handed in that would've been used during World War II, guns from the 1850s," Justice Minister Michael Keenan said.

"Among the more unusual firearms handed in under the amnesty have been a Beaumont Adams revolver circa 1856, a WWI era Lee Enfield rifle and two WWII US M1 carbines."

One farmer told the Herald Sun he handed in some of his family's rare weaponry because "there are some real bad buggers out there".

As part of the first amnesty since John Howard's scheme after the Port Arthur massacre in 1996, Australians have handed in approximately 464 firearms a day.

But there's a long way to go until some of Australia's 260,000 illegal guns are out of terrorists' hands.

"Unregistered firearms could fall into the hands of bikies," Mr Keenan told Sky News.

"Unregistered firearms could fall into the hands of someone else who could do the wrong thing with them."

The amnesty, which was announced in June, allowed people to hand in unregistered guns from July 1 and was a key outcome of the Lindt Cafe siege review.

Police confirmed 25,999 firearms had been handed in across Australia between July and September and urged owners of illegal firearms to hand in what was left before the amnesty comes to an end this month.

NSW surrendered the most firearms (13,468), followed by Queensland (7000) and Victoria (2150). South Australia (1338), Tasmania (1,136) and Western Australia followed (521).

"If you hold that gun after the end of the amnesty period then you are running a very significant risk," Mr Keenan said.

It is illegal to own an unregistered gun in Australia. Outside of the amnesty period, being caught with an unregistered firearm could cost you up to 14 years in prison or a fine of up to $280,000.

The amnesty runs until September 30.

"There are now only three weeks remaining to hand in firearms under the amnesty, and I ­encourage Australians to continue to take advantage of the ­amnesty period to help remove unregistered firearms from the community.

"As we know, just one firearm in the wrong hands can be deadly."

An incredible 643,726 firearms were handed in during the 1996 amnesty.

- Information about individual state and territory requirements, including how and where to surrender firearms, can be found at firearmsamnesty.ag.gov.au or by calling 1800 909 826.