A Vietnam-era flamethrower, automatic firearms and a crossbow were among almost 18,000 armaments handed over in the first year of a national weapons amnesty.
The program's annual report found 17,543 firearms and weapons were surrendered in the year to June 30, 2022, along with 606 weapons parts including suppressors and magazines.
More than 38 per cent of the 247 people who forfeited weapons said they did not have a gun licence.
Almost a quarter said they received the weapons as family heirloom or from deceased estates.
ACT police said they believed the surrendered flamethrower was used for training and not frontline service.
The amnesty was approved by the former federal government in 2019 and commenced in July, 2021, due to COVID-19 delays.
Attorney-General Mark Dreyfus said the amnesty was an important measure to reduce the number of firearms circulating in the community, and keep Australians safe.
"The report released today found Australians who surrendered firearms in that time period were primarily motivated to do so out of a sense of responsibility or because they did not require them," Mr Dreyfus said in a statement.
"The Albanese government thanks those Australians who have participated in the permanent amnesty and urges gun owners to continue to hand in their unregistered or unwanted firearms."
In 2016, the Australian Criminal Intelligence Commission estimated there were roughly 260,000 illicit firearms in Australia, but the exact extent of the country's illegal firearms market is unknown.
Australia previously implemented two weapons surrender schemes including a national buyback and amnesty scheme in the wake of the Port Arthur Massacre in 1996 which resulted in the surrender of almost 650,000 firearms.
A three-month amnesty in 2017 resulted in the handover of 57,324 weapons.
The report stated that unregistered firearms were difficult for law enforcement to trace and were an attractive target for crime syndicates, even if properly secured.
More than half of the 2425 firearms stolen in 2018 were safely stored.
The federal government said those with unregistered and unwanted firearms can surrender them anonymously and without penalty, with state-specific processes available on the Crime Stoppers website.
