The 18-year-old was targeted as part of Operation Unification, a national initiative to take illegal guns off the street.

Police said they seized a home-made pistol from the man on Friday afternoon.

The firearm was capable of firing and police believe he made two other guns, one of which has been recovered.

Investigations into the whereabouts of the third firearm are continuing.

Unification finished at midnight, having taken almost 80 firearms out of circulation, including two sub-machine guns.

Of the haul, 36 firearms were seized by police and 42 were handed in at amnesties around the state.

Nineteen of the seized firearms were unregistered with unauthorised possession.

The remaining 17 seized firearms were registered and further investigations are under way. Police conducted 45 targeted searches during the two-week operation.

Sixteen people will face court on firearms related offences as a result.

"A total of 78 seized and handed-in guns is an excellent result," Hobart CIB's Detective Senior Sergeant Craig Joel said yesterday.

"These firearms can't be used in crime, or targeted for theft by criminals.

"We would really like to thank those people who handed in guns voluntarily."

There is a permanent amnesty for handing in firearms in Tasmania. Under the Firearms Act 1996, any firearm can be handed into a police station and no further action will be taken in relation to possession offences.