I believe the 270 would get the job done with a good bullet like the accubond like RR stated. But you also stated you have the option of taking a 'heavier' rifle. If it were me spending my hard earned cash going after one of these tough critters, I would definately take a .30 cal mag with a good 180 bullet. The Accubond or Barnes XTS would be my choice in 180 gr.