Not too familiar with South Australian deer. But, if they're similar to the deer in the U.S., it's my understanding, you're looking for a minimum of 700 ft/lbs of energy upon impact to kill the deer.
Factory loads are typically designed for the upper end of the velocity for the specific caliber. For 180 gr loads, you're looking at nearly 3,000 fps muzzle velocity. According to JBM, a 180 gr projectile will bleed off enough of it's energy to deliver 1,435 ft/lbs of energy having crossed 600 yards, twice as much required to drop your deer.
If you were to reload, and chose 180 gr projectiles, you could charge them at the lowest and deliver 927 ft/lbs after firing 600 yards...far more acceptable if you want the meat.
I've heard of stories of hunters shooting deer with 300 WinMags and blew the haunches clean off the animal. The 300 Winny is capable of taking all North American big game. This includes moose, Kodiak and polar bear. Imagine what it'll do to deer!
BTW...for sh*tz and giggles, the boat tail has no effect on terminal ballistics...only exterior ballistics (helps with accuracy).
Good luck.