A Sydney mechanic who built a sub-machine gun out of Bunnings parts has been given a reduced jail sentence because of a legal loophole.

Samuel Kamo, 30, will serve a minimum of three and a half years behind bars, because the weapon was not in working order - simply because it had not been finished yet, according to The Daily Telegraph.

The .45 calibre gun was found during a raid on November 27, 2014, along with another home-made machine gun and a factory-made SKS rifle.

Sydney mechanic Samuel Kamo, 30, (pictured) who built a sub-machine gun out of Bunnings parts, has been given a reduced jail sentence because of a loophole

During their investigation of an Ultra-Tune store in Parramatta where Kamo was a manager, officers reportedly also found a homemade silencer, hollow point bullets and other weapons.

Kamo claimed following his arrest that he was forced to make the weapons for $5,000 by members of a Western Sydney gang who gave him a 'list of what to buy from Bunnings'.

Documents from court showed the weapons 'may have discharged cartridges', having tested positive for lead.

One of his lawyers, Abbas Soukie, said outside court that his client expressed 'unreserved remorse for his involvement in the crim' and was 'happy' with the verdict.

Kamo will serve a minimum of three and a half years behind bars, because the weapon was not in working order - simply because it had not been finished yet

Kamo pleaded guilty to charges of manufacturing and possessing unauthorised firearms, which can carry maximum penalties of 20 and 14 years respectively.

New South Wales Police Minister, Troy Grant, said there would be a review into the definition and whether it needed to be altered.

'Following the last meeting of Police and Justice Ministers, NSW is in the process of developing model legislation concerning firearms manufacturing offences,' a spokesperson for Mr Grant said.