A good Western invites you to glory in the leisurely tug of freedom, and also its opposite: the way that even the most rambling, loose-spirited men can be trapped, by circumstance, into picking up a weapon and using it with a vengeance. Open Range, Kevin Costner's enjoyably square new saddle-and-six-guns epic, opens with dazzling vistas of untamed big country -- the green of the grass just about glows, the clouds look painted by Winslow Homer -- yet the movie is, in essence, softening us for the kill. Boss Spearman (Robert Duvall), a grizzled veteran of the plains, and his tobacco-spittin' protégé, Charley Waite (Costner), have herded cattle together for 10 years. The two men cherish the stripped-down, nomadic rituals of their lives as if they were gypsies, yet they've been at it just long enough to feel that the rootlessness they've chosen is starting to strand them.
With gray in their goatees, they're the last of a breed -- aging cowboys known as ''freegrazers,'' who are stuck in the pre-Civil War era when land was unowned. The two run smack into the capitalistic heartlessness of the new West when they happen to tend herd on a patch of unspoiled terrain near Harmonville, a makeshift town controlled by a vicious, insult-spitting Irish rancher named Baxter (Michael Gambon). Baxter and his goons beat up one of Boss' underlings and toss him in jail, and the intimidation escalates from there.
With its laconic yet formal yup-and-nope dialogue, its overt lunge for Hollywood ''classicism,'' ''Open Range'' feels at times like the horse-opera equivalent of a Restoration Hardware boutique. Costner chews a bit too mopily on lines like ''He was the kinda man who'd say good mornin' and mean it, whether it was or not.'' And yet, directing his first Western since ''Dances With Wolves,'' Costner shows an exacting instinct for how to build a shoot-'em-up from the ground up. It's really the trashed spirit of American self-determination that sticks in Boss' craw. He can no longer ramble where he wants to, and for a cowboy living on his last fumes of wanderlust, that's death. Duvall and Costner play together like a seasoned team: They're wary, unsentimental colleagues whose opposing rhythms -- Boss is spiky and righteous, the mellow Charley is slower to anger -- never undercut their silent allegiance. These lone-justice heroes aren't shy about using their fists, or their rifles, but their drive toward violence gathers with an inevitability that walks the line between formula and fate.
Costner may have been going for the somber grandiosity of ''Unforgiven'' when he set the entire middle third of ''Open Range'' in a drenching rainstorm. The muddy deluge is atmospheric, but you miss the vigor and snap of a vintage Western. The supporting characters, on the other hand, are strictly old school. Michael Jeter, who died after the film was completed, plays the town stable owner as a scrappy fusion of Gabby Hayes and Walter Brennan, and Annette Bening, as the local doc's unmarried sister, makes love eyes at Charley like a saintly virgin out of John Ford. These are corndog roles redeemed by terrific actors. There's nothing corny, however, about the climactic shoot-out, which Costner has staged superbly as an extended logistical mini-war that surges and rifle-cracks with bloody abandon through what feels like every building in town. Call it dances with guns.