Sicen Sun, 28, was arrested in 2017 after he advertised one of his imitation weapons for sale for $1 million on a Facebook buy, swap and sell group.
He's since pleaded guilty to charges including possessing a digital blueprint for the manufacture of firearms, manufacturing a pistol without a licence permit, and possessing an unauthorised pistol.
"With 2020 hindsight I just realise how silly, idiotic, stupid and naive my actions were," he told his NSW District Court sentence hearing on Monday.

Gun safety advocates and law enforcement officials are appalled at 3D gun designs being online. Source: AAP
"I could not even begin to contemplate that a hobby would land me in such strife."
Sun, who dresses up as pop culture characters and was previously described by a lawyer as "something of a fanboy", said he meant for the replica firearms to be used as costume props.