Buck Harris is ready for the end.

When the banks collapse, or when the communists descend, or when the bomb drops, or when the cities erupt, or when the food is gone, or when nature goes beserk, or when chaos reigns and man turns to primal instincts . . . when one or more or all of these things happen--and this resident of Manchester, Md., is sure they will--Harris will head for the hills.

This former special forces sergeant and mercenary fighter will don the camouflage fatigues he sometimes wears to the market. He'll pick up the rifle he keeps on a floral chair in his living room. Then he'll put his family into his camouflage jeep and head for a farm, in a location he won't disclose, stocked with two years' supply of canned food and enough arms and ammunition to fight "a dirty little war."

"I'll survive," says Harris, 43, a former truck driver, former plumber and ordained fundamentalist minister, slapping one of his black combat boots with a swagger stick.

"Will you?"

Tens of thousands of Americans are asking the same question these days. From the mountaintops of the Sierra Nevadas to the rolling farmland of Carroll County, Md., survivalists are stocking up, battening down and preparing to hide out from Armageddon.

They are subscribing to magazines like Survival Guide, the June issue of which features a story headlined "Leave My House or I Will Shoot You." They are subscribing to newsletters like Howard Ruff's Financial Survival Report, formerly known as Ruff Times.

In Akron, Ohio, a woman recently received a concealed underground storage room as a Mother's Day present. In Denver, a survivalist food preparer holds tasting parties featuring powdered cheese, tomato crystals and textured vegetable protein. In Baraboo, Wis., about 50 adults tested their survival instincts in a field exercise: they armed themselves with BB guns, split into two groups and practiced taking away each other's food supplies. In Austin, Tex., a middle-aged businessman goes to sleep with $25,000 worth of gold pesos and krugerrands in his bedroom and a small arsenal of firearms and a six-months supply of food nearby.

A group of survivalists near Almosa, Colo., has built a 250-square-mile community of stone and adobe and is learning ancient farming methods from the Hopi Indians. In Utah, the construction of an underground condominium city is under way. And in the Midwest, one group of survivalists is working on antigravity spaceships that will leave Earth at the appointed time and orbit until the clouds of destruction have passed. Then they will land and repopulate the world with their super-educated children.

Harris himself is a member of Carroll County's "Chartered Sheriff's Posse Comitatus," a right-wing group. The 35 men in his posse meet weekly in the Sportsman's Barber Shop in Westminster, Md., and monthly for field maneuvers in the wilds. The men in the posse believe that the only true American sovereignty rests with individuals, not the government, and that the absence of God on the American political scene has rendered this country a doomed communist/capitalist state.

"We have enough common sense to know that we're not going to change the world," Harris says. "As much as I hate to say it, the world is going to hell in a hand basket. Maybe that seems like a pessimistic view, but we think it is a realistic one."

Harris says his own particular chapter will have no part of the rabid anti-Semitism, racial hatred and principaled tax evasion espoused by men like Wisconsin posse leader Jim Wickstrom, who has appeared on televison shows like Phil Donahue's. Or the violence that surrounded Gordon Kahl, who in early June was killed in a gun battle with police in rural Arkansas. Kahl, a 63-year-old North Dakota farmer, had been indicted by a federal grand jury in the shooting deaths of two federal marshals in North Dakota who were trying to arrest Kahl for parole violation on a tax evasion charge. Kahl had eluded police and been at large since February. His two accomplices were recently convicted of second-degree murder by a federal jury in Fargo, N.D.

Although survivalism does have its extremist fringe, the motivation of many survivalists in the country tends to be apolitical and nonreligious, though some of its roots can also be traced to the Mormon practice of stocking at least a year's worth of food as a hedge against economic hardship and to prevent dependence upon others.

The major motivation of most of today's survivalists seems to be economic: survivalists started hoarding supplies during the 1973 Arab oil embargo, then later began stashing gold as the dollar fell in value. In 1979, after the crises in Iran and Afghani- stan, many survivalists started buying guns and moving to rural hideaways.

If there is a fundamental theme running through survivalism, it is that man will emerge from the ashes of global ruination only if he heads for the country. The enemy will be the unprepared urban hordes who will rage out of the cities seeking food and shelter. Because of this belief, many survivalists refuse to admit they have well-stocked hideouts. If they do admit having hideouts, they usually decline to disclose the location.

In an extensive survey of nationwide survivalists, Survival Guide Magazine provides this portrait of its readers: 97 percent are males, with a mean age of 34; most are in the skilled-worker class or above, with an annual income of $25,000 or more; 76 percent are married; to a man, they are armed with one or more firearms; and 72 percent stock food and water.

Dave Epperson, the magazine's editorial director, says his readers range from "paranoids who live virtually underground in fear of virtually everything, to the light- hearted guy who wants to Daniel-Boone-it in the boondocks of northern Idaho. From people who wear nuke suits to bed at night to the guy who wears a fringed leather vest on the weekends."

In either case, Epperson says, his readers are "serious about survival." They are "people who would rather read about advanced paramedical skills than first aid, about foraging off the land than about buying survival food, about stealth tactics and snares than electronic security devices, about long- term food preparedness than nutrition."

Like any trend, Americans have jumped onto the survival bandwagon carrying fistfuls of cash, and hundreds of businesses have emerged to take advantage. Magazines like Survival Guide, the most widely read of about five magazines of its kind, are just one of the offshoots of the growing trend. Survival Guide's circulation tripled to 90,000 last year when editors shifted its focus away from the hunting and gun enthusiast market it held when it was called Shooter's Journal.

Included in the June issue are stories about meat preservation, burn treatments, cooking without utensils, building steam engines, and consumer reports on the Leatherwood ART/MPC Super Sniper scope and the Sterling Mark 6 carbine.

In his monthly editorial, Epperson writes of a weekend plan to head out to his place "at the edge of the desert/ mountains." (Epperson says, "One of the tools of the survivalist trade is not to tell anyone anything.") Once there, Epperson writes, he and his wife, Sally, will add some packages of dried milk and a couple of bottles of Tang to the food stash out at the place, shoot a couple hundred rounds of rifle and pistol practice and bag a rabbit or two "for practice.

"We plan our weekends around our survivalist leanings," Epperson writes. "We work to prepare and to harden our self-reliance skills. We enjoy these working weekends . . . By the way, what are your plans?"

Another big growth industry has been the survival food business. Companies like Park City Freeze Dry of Utah offer such delights as Pack-Away Freeze-Dried Crab Salad at $165 a case (210 one-cup servings per case), and Pack-Away Freeze-Dried Scrambled Eggs and Sausage at $103 a case (192 one-cup servings per case).

Builders are also getting into the act, equipping expensive retreat homes with bulletproof glass, lead plating, reinforced concrete, multifuel furnaces, underground shelters, storage areas and elaborate alarm systems. Some owners also want wood- burning stoves and refrigerators that run on kerosene. One Pennsylvania firm sells an exercise bicycle that is advertised not only as a bomb shelter fitness device, but also an electrical generator.

Book publishers have surfaced with the movement. Paladin Press, of Boulder, Colo., has been in business since 1970, publishing books on related subjects, including survivalism, martial arts and guns.

Paladin's "pivotal book," according to general manager Tim Leifield, was Life After Doomsday, by Dr. Bruce D. Clayton, which sold 30,000 hardback copies at $19.95. The paperback rights have been bought by a division of Doubleday. Also included in the Paladin Press lineup are Survival Poaching, Combat Survival and The Mini-14 Exotic Weapons System.

Says publishing manager Leifield: "I see the survival movement overall as a very healthy attitude, one of involvement rather than apathy. It's the kind of thing where, if there is one common thread, they don't believe that the government has the capability to provide civil defense and take responsibility for them, so they, individuals, are taking responsibility for themselves.

"A man's got to do what a man's got to do," says Posse member Harris. "God's got to be pissed at the world . . . and we love it. After all, it gives us something to bitch about. As you know, genuine Americans just ain't happy unless they are bitching over something."