The 9 mm F1 was a standard Australian submachine gun manufactured by the Lithgow Small Arms Factory . Issued to Australian army troops in July of 1963, it replaced the Owen machine carbine. The F1 was retired in 1991 and replaced by the F88C Austeyr, an Australian-built version of the Steyr AUG Carbine with slight modifications. The F1 had a robust and simple design and proved useful in close-quarters fighting during the Vietnam War.