Artem Vasilyev, 27, of Findon, in Adelaide's western suburbs, has pleaded not guilty to one count of committing other acts done in preparation for, or planning, a terrorist act.
A video recorded during an initial police search of Vasilyev's home, on August 20, 2021, was played to the jury at his trial in the South Australian Supreme Court on Friday.
Prosecutor Justin Hannebery KC has previously alleged Vasilyev researched methods to destroy the Cherry Gardens electrical substation, in the Adelaide foothills, allegedly motivated by promoting the cause of white nationalism.
The court has been told the former Defence electrical engineer frequented white supremacist chat rooms, sharing gun-building and bomb-making instructions under the user name "Panzer and Grettel".
During a search of Vasilyev's home in August 2021, a police ballistician identified weapons and gun parts around the home.
In the video played to the jury, Detective Brevet Sergeant Chris Walkley, of the Serious Firearm Crime Investigation Section, told the accused it "appears evident that you're manufacturing firearm parts using a 3D printer".
Vasilyev replied: "It certainly wasn't my intention to make functional firearms ... I thought what I was making was just a model."
During the search, police found an improvised AR-15 semi-automatic firearm produced by a 3D printer. There was also a box containing 3D-printed gun parts used to make an FGC-9 firearm.
In the video, Sgt Walkley tells Vasilyev: "So someone sent you the plans for the FGC-9. Do you know what the FGC stands for?"
"I don't know. It's some sort of acronym, I assume," Vasilyev replied.
Mr Hannebery previously told the court that FGC stands for "F*** gun control".
Referring to parts produced by the 3D printer, Vasilyev told the detective that "I was trying to make sure they wouldn't be operable".
"I got these plans ... I thought this was just a toy, essentially. I didn't really realise that this would be a working firearm," Vasilyev says in the video.
Sgt Walkley advised Vasilyev that he would be arrested for manufacturing firearms and other firearms offences. He told him he would be taken to the Adelaide city watch house where DNA samples would be taken before he could seek bail.
When Vasilyev asked if he could refuse to give DNA, Sgt Walkley told him that "reasonable force" would be used to carry out the procedure if he refused.
"It sounds like the answer is 'no'," Vasilyev replied.
Asked if he had a current passport, Vasilyev said: "No. I came here on a Russian passport as a kid and it's long since expired. I can't escape either way."
Scott Henchcliffe, for Vasilyev, confirmed with Sgt Walkley that as a result of the search, Vasilyev was charged with firearms offences and later pleaded guilty to 22 offences.
Mr Henchcliffe previously told the court that his client did not deny having an interest in firearms, but it was "inherently absurd" for the prosecution to suggest his client wanted to blow up a substation to advance the cause of white nationalism.
The trial, before Justice Sandi McDonald, continues on Monday.
