There were quite a few .22 calibre ones (including full length versions), 6mm or .243/303, .25/303. the . 270/303 which you have there. These were all the rage up until the late 60's or early 70's when imports from England (Parker Hale, BSA etc) & America (Winchester, Remington etc) became very popular & these literally just disappeared. I have heard of a .35/303 & even a .375/303, but can't recall seeing these calibres back when I was a young fella!
From memory Super & Riverbrand Cartridge Companies used to make loaded rounds.
You have a fairly rare bird there mate, I haven't seen or heard of anyone having or reloading one in years!

remarkable, when such things are discussed here its sounds like such rifles standing half forgotten in every third shed in australia but it seems they were allways rare