Aiden Marton Takacs, 26, has been charged with seven firearms offences after police allegedly found replica pistols, swords, daggers and knuckle dusters in his bedroom.

In court, Takacs' defence lawyer Matthew Ward said his client had a "fixation and obsession" about how the firearms worked and he enjoyed taking them apart.

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Mr Ward said Takacs suffered from mental illness and high-functioning autism.

He said his client purchased the pistols online, noting Takacs' family were "frustrated" by how easy it was for replica guns to be purchased online as they were often marketed as toys and were inexpensive.

Mr Ward said his client did not have a criminal history nor did he intend to harm anyone or use the firearms.

Magistrate Michael O'Brien granted Takacs strict conditional bail noting his mental health and that it was his first time before the court.

Documents tendered to court revealed police went to Takacs' family home for an unrelated domestic violence incident on Sunday.

After speaking to Takacs' parents, officers tried to locate him inside his bedroom, however he was not there.

Officers looked inside the bedroom and allegedly saw a number of weapons and firearms in "plain sight".

During the search, police allegedly found and seized three air pistol firearms, two of which were fitted with magazines capable of firing small projectiles, as well as Gel Blaster ammunition.

While searching under Takacs' bed, police allegedly found a military-style air rifle, and a Uzi-style air firearm with magazine attached.

Homemade and bought fireworks were also allegedly sitting on the wardrobe. The fireworks varied in sizes and shapes and were allegedly found in various drawers, under Takacs' bed and laying throughout his bedroom, as was a large roll of detonator cord.

Knuckle dusters, swords and daggers were allegedly hanging on the wall above the bed head. A slingshot made from a wooden and metal frame with a high-powered elastic cord attached was also allegedly found.

Lake Illawarra police arrested Takacs a short time later and charged him with possess, supply or make explosives for unlawful purposes; two counts of possess unregistered prohibited firearm; three counts of possess unauthorised firearm and possess or use a prohibited weapon without permit.

Police documents allege Takacs admitted to owning the firearms and explosives, however during an interview stated there was "no malice" behind it as he used them as toys and had the fireworks for "personal use".

The court heard, Takacs did have an active firearms licence but it had been suspended following his arrest.

As part of his bail conditions, Takacs will be required to live at a friend's home in Windang, will have to report to police twice a week, must see his doctor and must not acquire or manufacture a weapon or firearm nor visit a website where they can be purchased.

The case will return to court on February 2.

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