I chose the .495 A-Square for a rebore project of a Ruger RSM .458 Lott. Couldn't be happier with the results. I found dies at CH4D, brass from Superior Reloading and ordered a custom reamer from Pacific Tool. Not sure if any of this helps an Aussie.
The big Ruger is a good weight for the .495, and with a .416 Rigby magazine and follower, the conversion was fast and feeding is perfect.
My use is at .500 NE ballistics, 570 grains at 2,150 feet from the 23" barrel. The rifle is off being stocked now. Stocked for point and shoot with open sights. Finished weight target is 10 lbs
5 ozs. I'm planning another Africa trip for 2017, and having two good buffalo already, I want to cull 2 or 3 cape buffalo on a SA game farm. Maybe the outback next time.
If you choose the .495, you will love the feel of it in your hand.