It comes as something of a shock to find Richie Cunningham and Barnaby Jones teamed up in desperate battle against the American military establishment -- and in a TV movie from Johnny Carson's production company, besides. If the picture had been produced during the '60s, it would doubtless have been denounced as hysterical liberalism, yet now it has the trappings of a Reagan Republican manifesto.

In "Fire on the Mountain," the NBC film at 9 tonight on Channel 4, Buddy Ebsen plays an ornery New Mexico rancher who refuses to sell his property to the U.S. Army so it can use it for access to a new mobile missile base, then refuses to vacate the property when the government seizes it anyway. Ron Howard plays a young land speculator who takes a shine to the old codger and finally begins to see things his way.

Unfortunately, the dramatic potential of the story is all but frittered away in director Donald Wrye's stubbornly pokey first hour. He almost heads himself off at the impasse. But the final stand-off, with Ebsen sitting on his front porch with a rifle in his hands, and the army massed in his front yard, is still murderously suspenseful.

It also represents a new wrinkle in video Americana. Howard continues to make the transition from the wholesome nebbish of "Happy Days" into an actor of sly intensity, and he keeps taking roles that put him opposite the authority symbols Richie wouldn't have dreamed of opposing. Ebsen is known for his conservative political views and for playing noncommittal cusses like Jed Clampett and private eye Jones; yet here he is in a film that says those in power can be miserable curs.

He also has a speech about there being too much government that, one assumes, the White House would greet with a hearty hoorah. In a Frank Capra movie of the '30s, Ebsen would somehow have won his battle -- perhaps with the help of his neighbors -- but in this film, he loses. The denouement is daringly a downer, especially for prime-time network TV during the November sweeps.

John Sacret Young's script simply doesn't summon up sufficient wallop, however, and the static pacing really does the film in even before the conflict with the army is articulated. Still, Howard and Ebsen are a formidable team, ably assisted by Julie Carmen as a Mexican American housekeeper and young Rossie Harris as Ebsen's worshipful grandson.

The producers were thoughtful enough to hire Basil ("Blue Lagoon") Poledouris to do the music and the resourceful Woody Omens to handle the cinematography. Omens captures the stark beauty of the locations and such nuances as a Christmas morning lit by the glow from a fireplace. The film is visually passionate and dramatically pale. As a sign of the times, it is haunting and perplexing.