Geeze I hate to sound so ignorant but never having hunted in Australia I noticed that most game opportunities for hunters were probably 100 pounds or lighter. I noticed a rifle in the movie, "The Man from Snowy River" that looked like a lever action centerfire .22 of some sort. (Ain't it wonderful when you get impressions from movies as if those guys know anything about guns?) Or a guy who is so gun crazy that he notices stuff like that in the first place? Actually I wasn't surprised by the response because where I hunt most of the time in Kansas is probably quite similar to the Eastern and Western sections of Australia and our game is probably similar in size to yours in those areas (coyotes, whitetail deer, mule deer, American pronghorn and a few feral hogs) Any of the rifles in the .22 range that you mentioned will do quite nicely here. And the .243 will easily do it all for this class of game.