The Leader T2 MK5 Series firearms were chambered for the 5.56×45mm NATO cartridge and manufactured by Leader Dynamics of Smithfield, NSW, Australia (1978-1982/1983). The Leader was the brainchild of British weapons designer . It was originally a contender for a 5.56 mm Australian military service rifle to replace the then-issued Lithgow L1A1-F1 SLR and Colt M16A1 rifles. What was unique about this endeavor was that Australia had never designed or manufactured its own commercial gas-operated semi-automatic rifle. The rifle was abandoned when the Steyr AUG was adopted for use by the Australian military.