My buddy, who also has a 270 AM, has access to some private land through the outfit he works for just outside town at the edge of the sagebrush. We can shoot out to 800 yards there.
I also shoot up in High Valley (L T Murray) and there's a few places where we shoot up in the hills on Chinook pass. A lot of times we just drive the hills looking for long range rocks that need busting.

There's a ton of places like that, it's the places where target setup and access is easy that are hard to find sometimes.