From a cartridge discussion forum – Between 1948 and 1975 restrictions were placed on private citizens in N.S.W. from owning military rifles unless they were landowners or members of a military rifle club. In the early 1960’s, to get around this it was Jack Pollard, a gunsmith from Sydney, cut one full thread from the chamber of a Lee-Enfield barrel and rescrewed it to the action creating a new cartridge. The standard .303 case shoulder was pushed back about 2 mm. They tried to prosecute him but he was let off on a technicality due to a tape recording he made of impropriety(?) by the NSW government. Many of these rifles had loose chambers and could also accept 303 British rounds.

The box below is from The Super Cartridge Co (Maribyrnong, which was situated at 151 Raleigh Rd. Melbourne, Victoria). They were in business until the late 1970’s until the company failed to restructure after losing a patent infringement lawsuit against Olin and was taken over by Bruce Bertram in 1982.