You wont find much in the way of ranges. I head out past matlock into the national forest there and can get longrange shots on rocks and things going across canyons. There is some places in capitol forest as well I have heard but havent found them yet.
I'll second the vote for national forest land or some of the private timber land that you could access via logging roads. Its gonna take some scouting to find a decent spot but one you find a good landing or vantage point you can set up multiple targets at various ranges. We do something similar up here on state DNR land; we just leave out steel targets out but lay them down or chain them to a tree in some locations. That way there is minimal setup and we can drive out to the target locations.