Owen, an inventor from Wollongong, was 24 years old in July 1939 when he demonstrated his prototype .22 calibre "Machine Carbine" to Australian Army ordnance officers at Victoria Barracks in Sydney. The gun was rejected for two reasons. The first was because the Australian army, at the time, did not recognise the value of submachine guns. The second was the basic construction of the prototype was completely unsuited as a military weapon, especially as it lacked a proper trigger or any safety device, was of small calibre, and the "magazine" was effectively a giant revolver cylinder which could not be exchanged to reload. Following the outbreak of war, Owen joined the Australian Army as a private.