NATRONA COUNTY, Wyo. — The row of machine gunners sprayed a steady stream of bullets hundreds of yards downrange into the Wyoming prairie, destroying propane tanks, fire extinguishers and the occasional stick of dynamite or sacrificial radio-controlled model airplane.

These enthusiasts were celebrating machine guns and machine gun rights — and they've been doing so annually at the Northern Rockies Machine Gun and Cannon Shoot, whose 2011 edition was held recently at a ranch west of Casper.

“A lot of people give us a bad rap and say, ‘Why do you need a full-auto gun?”‘ said Quinton Miller of Casper, one of several dealers offering machine guns for rent. “Well, because we can.”

The shoot featured a wide array of machine guns and earsplitting noise: Large ones on tripods pulsed with a profound thumping bass. Small ones, designed to fit under suit coats, emptied their magazines with jagged rips of sound. Gunners wore both foam ear plugs and ear phones to prevent hearing damage from the wall of sound.

With both hands on the twin wooden handles of a tripod-mounted machine gun, one shooter simultaneously pulled back on a safety toggle with two fingers while pushing forward with both thumbs on a plunger that serves as a trigger.

The gun fired, moving on its tripod with a surprisingly gentle, rocking motion, sucking a belt of loaded cartridges in one side and spewing smoking, empty casings out the other. Through the peep sight, bullets kicked up puffs of dust on the landscape. Smiling shooters exchanged high-fives and posed for pictures next to their weapons.

Although machine guns are designed solely to kill, they are also are marvels of mechanical engineering — something celebrated at the Wyoming shoot. They harness the gas pressure or recoil of each cartridge as it fires to cycle the action, eject the empty casing and feed in a fresh cartridge.

Demand for machine guns went up sharply after Congress banned sales of new guns to civilians in the mid-80s. The government taxes each machine gun transfer $200.

With the supply of guns fixed, it can cost $12,000 to $15,000 to buy a gun like Bill Hudick's World War I-era .303-caliber Vickers. Buyers must apply for and pass a federal government background check. Hudick and other shooters emphasized that legal, registered machine guns aren't typically used in crimes.

It's also expensive to shoot them at the Wyoming event, and others held across the country. “You're talking $300 to $500 a minute to shoot one of these, so it will definitely keep you out of the bars,” said Hudick, who works in the excavation business in eastern Colorado.

Several shooters said the fact private citizens can own machine guns underscores a unique level of personal freedom in the United States.

Robert Mullen, a Korean War veteran from Sheridan, said the shoot showed that Wyoming is one of the last bastions of a rare kind of freedom — one combining vast stretches of unpopulated land with full acceptance of gun ownership.

“It's still open yet, and people still have a choice. They can make up their own mind,” Mullen said. “They still have their own free will, or whatever you want to call it. I don't know how long that's going to last.”

Miller said people commonly respond with suspicion when they hear about his interest in machine guns. He said his work with the oil industry has taken him to Kuwait and elsewhere in the Middle East, where people are dumbfounded to learn U.S. citizens may own machine guns.

“We don't know how good we have it,” Miller said.

Event organizers prohibited vendors from renting any machine guns shorter than 18 inches. An 8-year-old boy died at a Massachusetts machine gun shoot in 2008 when he lost control of a 9 mm micro Uzi and shot himself.

Here, passers-by were able to pay $20 to $30 to fire off a magazine or a belt of cartridges.

“They're just fun; there's not much else you can say about them,” Miller said. “Especially belt-fed guns, the ability of having more than 30 rounds.”

Matt Hendrickson of Laramie, a worker at the University of Wyoming, blazed away with a few different rental guns.

“It's something you don't get to do every day,” he said.

Jerry John Lovik, a dealer from Iowa, enticed members of the crowd to rent his guns with all the enthusiasm of a carnival barker. He brought 40,000 rounds of ammunition for the event, which he said was becoming more popular as others in Colorado and elsewhere close as locations become unavailable.

“My dad started me in guns when I was about 4 years old,” the 52-year-old Lovik said. “I guess you could just say it was a continual upping of the bar, is what it was.”

While other guns blazed on the line, Hudick's old Vickers momentarily sat silent on its tripod. Its action stood open. Water oozed from a corrugated metal reservoir surrounding the gun's barrel. A pile of spent cartridge casings, along with a few dud cartridges, littered the ground.

Hudick worked to replace a broken firing pin spring. His hands slick with grease, he fit the nearly century-old pieces of his gun's bronze and steel firing mechanism back together.

“If this was a real battle, that would be the point where the enemy would come up and blow my brains out,” Hudick said. “And that would be the end of Bill.”