The only places I know of are either the Pawnee grasslands (just get a good map, find a spot, & shoot), Pawnee Sportsmans Club (200 yard range, semi-private, 30 min east of FtC on Hwy 14), and there is supposedly a place near Bennett but can't remember the name and have never been there.
I belong to the Golden Gun Club which has a range at the Watkins exit off I-70 east of Denver. 100-200-300-400-500 (might be off a little) berms. Not "real" long range but will get your loads tested for accuracy
Pawnee is prety good, I like to shoot there, there is a makeshift berm for shooting, plus you can shoot anywhere safe, ocasional chance for the yotes as well out there. Beware there are a few jerks (nearby land owners & hunters) that will harass you for shooting out there trying to tell you that you cant etc..... However it is a NF and perfectly legal to shoot.