Moonshine now contains a measured resource of 53.9 million tonnes at 66% concentrate grade and an indicated resource of 218.7Mt at 66.1%, plus an inferred 997Mt at 64.6%.
Head grades range from 27.5-30.8% iron.
Macarthur's previous resources for Moonshine were all inferred at 710Mt, and have been upgraded following infill drilling last year.
The resource upgrade follows its proposal for development of a commercial track access agreement that would see Arc Infrastructure provide capacity on its network to support Lake Giles' link to Esperance Port.
The dual-listed junior recently lodged applications to develop a haul road and rail siding near Lakes Giles.
Executive chairman Cameron McCall said the access agreement advances, and upgrades for the Moonshine and Moonshine North resources, meant the company was "edging closer than ever to making this project real for shareholders" in the current commodity cycle, where iron ore is trading around US$120/t.
The company previously announced it was looking at early revenue generating iron ore operations, including a possible acceleration of development of its Ularring hematite project, also at Lake Giles.
Macarthur shares were last traded at 25c, valuing it at $25 million.