My "roo rifle" would be my .222's. Rem 788 and Mauser M03.

In the 'good old days' the .243 and the .22/250 were probably the go to choices. And the rarer .220 Swift. The .222 as well of course.

Nowadays the boring .223 is probably it.

Roo code of practice? I believe that is state based, NSW? Maybe Vic? Maybe applied for professional shooting for human consumption?

If I shoot roos, I certainly don't have to brain shoot them. The bs code of practice claims brain shots only for minisation of cruelty reasons. Dangerous stuff if ever applied to all hunting. Brain shots make sense commercially, minimise hide and meat damage.

If shooting on destruction permits, the carcase is left to rot on the ground. A waste. So chest shots are fine.

A .22/250 with a 55 gr fragile bullet allowed chest shots without an exit wound. Or a 50 gr bullet. Flat shooting. Accurate for head shots.

A .243 with a 70 gr HP was another choice.

.25/303 in the good old SMLE days.

I believe a .22/303 was available as well.

Converted SMLE's probably lacked accuracy.