The Nosler Partition is a good bullet, but I see no reason not to use whatever premium bullet you are used to shooting and even one of the bonded plastic tipped bullets. Something heavier would be preferable for the warthog, but its not a necessity. I'm sure Woodleigh do some good 6mm weldcores that I assume would not be too pricey as you are in Oz. Thousands of Springbok and Impala have been shot with .223 and I bet jackals too, so you should do fine with a 6mm (.243).