Sydney-based Sicen Sun, 28, is facing possible jail time after pleading guilty to charges of manufacturing 3D-printed firearms without a licence, and possessing an unauthorised pistol.

Sun was arrested in 2017 after he advertised one of his imitation weapons for sale for A$1 million via a Facebook buy, swap and sell group.

The replica SIG Sauer P250 pistol was advertised for three days on a group for military items. Two weeks later police arrived at Sun’s home with a search warrant.

“With 20/20 hindsight, I just realise how silly, idiotic, stupid and naive my actions were,” Sun said during this week’s NSW District Court sentence hearing.

“I could not even begin to contemplate that a hobby would land me in such strife.”

Sun’s barrister said there was never any suggestion the weapons were intended to be “anything but replicas” nor was there “any intent to make them into functional weapons”. Judge Penelope Wass said she is considering an “intensive correction order” for Sun, meaning any jail time might in fact be served in the community. The case is expected to return to court later this month.