about half the state of wyoming is open (pubic land) and you dont need to ask anyone for permission
starting at about the 3 hour to 3 and a half hour drive time from denver you can truly be in the middle of no where
local front range and east of here is tough access, you need to take a saturday/sunday and just start knocking on doors, I did that about 4 years ago and scored two farms that let me shoot p dogs and anything else they need shot.