I know several of my Appleseed brothers who have hit their targets at 1000+ yards, one that did it (1100+ yards) using a sling in prone without bipod, or bags.
http://americanshootingjournal.com/precision-long-range-shooting-the-coriolis-effect/#07tbowhf (http://americanshootingjournal.com/precision-long-range-shooting-the-coriolis-effect/#07tbowhf) :---