Escape From Chicago: Wyoming Firearms Founder Makes World’s Most Powerful AR-Style Rifle

Greg Buchel was born and raised in Chicago but “escaped Illinois” to move to Wyoming and founded Big Horn Armory which touts its AR500 as the world’s most powerful AR-style rifle. Buchel says it will down anything from "pachyderms to Peterbilts."

Mark Heinz

December 24, 20236 min read

Giant AR15 shooting 12 22 23
(Big Horn Armory via YouTube)

When it comes to bagging big, dangerous critters, hunters want all the knockdown power they can get, and a Cody-based company has taken that to the extreme.

Big Horn Armory Inc. touts its AR500 as the world’s most powerful AR-style rifle. The semi-automatic weapon is chambered in the company’s own .500 Auto Max cartridge and can thump out half-inch diameter bullets just as fast as a shooter can stand to pull the trigger.

“Bison are pretty much the toughest critter on this continent and it punches right through both sides of them,” Greg Buchel, the company’s founder and president, told Cowboy State Daily.

Escaping Illinois For Wyoming

Buchel wasn’t born in Wyoming, but said that he couldn’t feel more at home in the Cowboy State. He was born and raised in Chicago, and already had an extensive background in manufacturing before he moved to Wyoming more than two decades ago.

“I moved out here about 21 years ago. I escaped Illinois and I haven’t looked back since,” he said.

He enjoys the wide-open spaces, freedom and hunting opportunities the Cowboy State provides. And he also appreciates the business-friendly atmosphere.

He wasn’t in Wyoming very long before opportunity came knocking.

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Upping Smith & Wesson’s Power Levels

“When I first moved out here, a neighbor of mine was a gun crank. The .500 Smith & Wesson Magnum cartridge had just been created. And we thought, ‘Hey, we should make a lever-action rifle chambered for the .500 Smith & Wesson.”

So the seeds were planted for Big Horn Amory. The company was founded in 2007, and started turning out its first lever-action rifles a couple of years later.

Smith & Wesson created the .500 cartridge for its legendary revolvers. It dwarfed even the mighty .44 magnum. That round made Smith & Wesson a household name — thanks in large part to Clint Eastwood’s “Dirty Harry” movie character packing a Smith & Wesson .44 magnum revolver.

Cartridges like the .44 magnum and .500 Smith & Wesson are certainly respectable powerhouses in their original revolver platforms. But there’s a long tradition of building lever-action rifles chambered for magnum revolver cartridges.

The longer barrels take the bullets’ performance to whole new levels, Buchel said.

With their shorter barrels and gap between the cartridge chambers and barrel, revolvers blow out a fair amount of unburned powder when they’re fired.

The enclosed action and longer barrel of a rifle allow more of the gunpowder to burn, Buchel said. And more powder burned explosively during firing equals more velocity, and more bullet velocity means more devastating impact on the target.

Muzzle velocity, or the speed the bullet is moving when it leaves a firearm’s barrel, is measured in the feet per second (fps). So, for instance, a 400-grain bullet fired from a revolver might have a muzzle velocity of 1,457 fps. Whereas out of a rifle with an 18- to 20-inch barrel, it might be trucking at 2,000 fps, Buchel said.

An AR For Any Critter

Big Horn Armory’s popularity was growing among Wyoming hunters who wanted something that could stop a charging grizzly, if need be, as well as folks headed to Alaska to hunt huge game like moose and coastal brown bears.

Meanwhile, the popularity of AR-style rifles continued to grow. AR stands for “Armalite Rifle” after the company that first produced the firearms. And the most common chamberings for ARs are the relatively small .223 Remmington, or the 5.56×45mm NATO.

But ARs were also gaining popularity among big-game hunters who wanted them chambered for beefier cartridges, such as the .308 Winchester.

So, Big Horn Armory figured, why not produce an AR chambered big enough to take down anything that might lumber across North America?

Working off the .500 Smith & Wesson template, they designed the .500 Auto Max cartridge. It’s essentially a rimless version of the .500 Smith & Wesson, Buchel said, which allows it to feed property in a semi-automatic action.

“Lever-actions require a rimmed cartridge (one with a lip around the base), but semi-automatic actions operate with a rimless cartridge,” he said. “As an AR cartridge, the .500 Auto Max is our baby.”

A semi-automatic firearm fires one shot for each pull of the trigger, and the action cycles itself between shots.

The AR500 is designed as a hunting rifle because everybody who works at Big Horn Armory is a hunter,” he said.

Some of its features include a generously-sized trigger guard, making it easier to shoot with gloves on during cold weather hunts.

“We say it’s suitable for everything from prairie dogs to pachyderms to Peterbilts,” he said.

The latter being a reference to the rifle’s ability to punch through engine blocks.

  • The AR500, touted as the world’s most powerful AR, is made by Big Horn Armory, Inc. in Cody and chambered for the company’s .500 Auto Max cartridge.
    The AR500, touted as the world’s most powerful AR, is made by Big Horn Armory, Inc. in Cody and chambered for the company’s .500 Auto Max cartridge. (Photo Courtesy Big Horn Armory)
  • Giant AR15 exploding milk 12 22 23
    (Big Horn Armory via YouTube)
  • Along with the AR 500 semi-automatic, the Big Horn Armory in Cody builds high-end, magnum-caliber lever-action rifles.
    Along with the AR 500 semi-automatic, the Big Horn Armory in Cody builds high-end, magnum-caliber lever-action rifles. (Photo Courtesy Big Horn Armory)

Won’t Ruin Smaller Game

The company’s lever guns have been taken on South African Safari hunts. However, it’s unlikely that the AR500 will be used on Safari, because semi-automatic rifles aren’t allowed in South Africa, Buchel said.

Even so, it’s suitable for Wyoming hunts, he said. Folks might worry about such a massive round making a complete mess of relatively smaller animals, such as deer or antelope.

But with hard-case bullets that’s not the case, he said.

He knows of one hunter who used an AR500 to shoot an antelope, and said the critter “was dead before it even fell completely over.”

“There was a half-inch entry wound, and a half-inch exit wound” indicating that the bullet didn’t expand inside the antelope as smaller-caliber bullets would have done, he said

“But with a half-inch bullet, how much expansion do you need?” he added.

Big Horn Armory’s rifles are higher-end, but represent a long-term investment because of the craftsmanship that goes into each one, Buchel said.

The AR500s are priced around $2,500, and the lever guns are priced around $4,500 on up.

Promoting Wyoming Manufacturing

Buchel said he’s not only happy that his company has thrived in Wyoming, he’d like to see manufacturing continue to grow here.

“As a company, we’re growing. We can’t build them (rifles) fast enough,” he said.

And manufacturing can continue to add well-paying jobs to Wyoming’s economy, and help retain the state’s youth, Buchel added.

“In Wyoming, we sometimes say that we import retired people and we export our kids,” he said.

Mark Heinz can be reached at

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Mark Heinz

Outdoors Reporter