I have taken quite a few mulies with the 25-06 and the 270. Two of my favorite cartridges for that purpose. However my my expierence the 270 is a far better choice for big deer. In all my years of using the 270, I have not nor even considered using it for varmits. I will agree that there is no reason it wouldn't work but as a dual purpose deer/varmit, the 25-06 would be my choice. But on another note, I feel the 270 is efficient for elk and moose as well. Just use the right bullet.