If one is after our Beldings ground squrrels here in eastern Oregon, there are some guides available (surf up ground squirrels and Crane, Oregon). One would get more and better shooting though on his own, and a polite introduction and request from most alfalfa growers will result in a positive response.
For 5 or 6 hours of shooting, I load my 22LR in single shot mode and go through a little over a brick a day. In a good season, I will do 7 to 10,000 rounds, and simply can't afford to go the center fire route. If one can demonstrate proficiency, there are some land owners that will offer up ammo.
My most efficent approach is sit in a low-boy lawn chair with a bipod in front. Stay put until everything in reach is cleared out. Moving and walking around will put those within 22 LR range down for about 5 minutes. Many shoot from their rigs, but wet soils might limit ones access to field perimenters. I also dope the wind much better if I'm out in the elements where I can sense direction and velocity. Do bring some winter clothes, as we don't really have spring weather until about mid-June.
Rimfire action does not seem to bother them outside of 10 yards or so. Season is March, April, and into mid May when herbage gets too tall to see them. Foul and windy weather can put them down for days at a time though.
Equip with as much scope power as possible, as low end stuff pretty much covers a squirrel out past 70 or 80 yards. When youngsters emerge, they are literally about the size of a house mouse.