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“I like big guns and I cannot lie…”

It’s funny, need I say strange, the things that can run through a writer’s mind when trying to start an article… for some reason a remix of Sir Mix-A-Lot’s 1993 Grammy-winning, double platinum “Baby’s Got Back” hip-hop tune started playing in my head when pondering Big Horn Armory’s half-inch-bore AR pistol. I thought it might be fun to write a lyrical parody of the hip-hop song featuring this manly pistol, but after I read through the song’s original lyrics I had to stop and take a mental shower. To halt the song playing in my head, I got up from my laptop and went to refill my coffee cup….

Big Horn Armory, the Cody, Wyoming, rifle maker specializing in crafting .500-caliber lever-action rifles, decided to delve into the AR market. When they jumped in this overcrowded gun niche, their “go big or go home” approach left them with the “the most powerful AR on the market,” in their own words.

“We like to think BIG at Big Horn Armory. As a result, we’re not your average gun manufacturer. Since we’re gun guys like you, we only build guns that give us a reason to jump out of bed in the morning. For us, that means the bigger the better. Whether it’s packing 36,800 ft.-lbs. of energy in a lever action, or building the most powerful AR on the market, our goal is to give you the biggest bang for your buck. Literally. At the end of the day, that’s why we’re in the business. To build guns you can’t wait to shoot. We are so excited to have you join us on our quest to ‘Go Big or Go Home!’”

The Bullet

The 500 Auto Max is a rimless 500 S&W Magnum that offers shooters the option of buying factory fodder or reloading this behemoth. A very versatile cartridge, it can be had in loaded ammunition with bullets ranging from 280 grains up to a hefty 600 grains.

The handloader has even more options when utilizing bullets ranging from 275 grains to 700 grains. Bullet styles range widely, with, hardcast, jacketed hollow points, monolithic solids and more made available.

This range of bullet weights and designs make the AR500 suitable for anything from prairie dogs to pachyderms to Peterbilts, which offers semi-truck-stopping power in a platform weighing less than 10 pounds.

To give you an idea of this pistol’s power, let’s dig into some basic energy calculations. Bullet energy KE (in foot-pounds) is equal to the bullet weight (in grains) multiplied by the square of the bullet velocity (in feet per minute) divided by 450,437.

That being said, if you push a 440-grain Buffalo Bore flat-nose, gas-checked cast bullet out of this pistol at 1,650 fps, that yields a whopping 2,659 foot-pounds of energy. By comparison, a 240-grain .44 S&W Magnum factory load produces about 750 foot-pounds of energy. The insanely hot Buffalo Bore 340-grain Lead Flat Nose +P+ load launches at 1,425 fps from a 7 ½-inch revolver to produce 1,533 foot-pounds of energy.

Steinel’s 280-grain Brass Spike produced a 1.613-inch 5-shot group at 50 yards. Photo by author.

Gun details

Big Horn Armory’s AR500 semi-auto pistol is based on their ground-breaking AR500 Rifle, the most powerful AR-platform firearm available. The AR500 Pistol is a large-frame AR chambered in 500 Auto Max. This cartridge in combination with their AR500 Pistol puts a lot of power into a pleasant shooting, rapid firing, exceptionally compact firearm.  This combination of size, maneuverability and energy on target make the AR500 pistol easily accessible and ready to handle almost any situation.

Starting at the business end, this pistol sports a 10-inch Green Mountain barrel with a 1:24-inch twist. The muzzle is threaded ¾-28 TPI for an attached muzzle brake, or any other accessory you may wish to attach.

This pistol sports a top rail with full-length Picatinny slots for sight mounting. Fore and aft on the handguard it sports short Pic rail sections for more accessory mounting. A blade-style stabilizer is mounted on the recoil spring tube. An Ergo pistol grip helps manage recoil, too. An ambidextrous safety give easy access to either right- or left-handers.

A scorching 350-grain jacketed hollow-point loaded by Buffalo Bore produces about 20% more muzzle energy than a 12-gauge slug, and it produced a 1.435-inch 50-yard group. Photo by author.

Down Range

To wring this pistol out I mounted a Trijicon Ascent 1-4×24 scope for a little precision work. Later, I mounted a Trijicon RMR for a little sleeker outfit for moving and shooting on steel.

I managed to get my hands on two loads for the .500 Auto Max. The first was Steinel’s 280-grain Brass Spike. This load travels down the pipe of an AR500 rifle at 2,215 fps, but the pistol version sent these chunks of brass downrange at just a hair under 1,900 fps. At 50 yards this bullet’s best group measured 1.613 for five shots. Cut the distance in half and you’ll probably obliterate your aiming point with a tight cluster before you get to the fifth shot.

The second load was a Buffalo Bore 350-grain jacketed hollow-point +P+ that travels from a rifle at 2,300 fps and produces 4,110 ft/lbs of energy at the muzzle. The shorter barrel of the AR 500 pistol will slow this round to an average of 1960 fps. At 50 yards, this load’s best performance put five rounds into a 1.435-inch group.

The AR 500 Auto Max pistol is an amazing piece of hardware when you start flinging soup can-sized projectiles down range. And, just as amazing is its inherent accuracy with a big thump on the receiving end. Check one out, you’ll be glad you did.

Big Horn Armory moved to a new factory. Check out the news here.


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  1. The pachyderms in my neighborhood like to wear prairie dogs on their heads as sentinels when they raid my melon patch. I obviously must have at least one of these…

        • Sorry for the whimsy, but what sent me off into fantasy land was this –

          “36,800 ft.-lbs. of energy in a lever action…”

          Given that a 700 Nitro ‘only’ has about 9000 ft/lbs, it is an obvious typo, but the image sorta mlgot me going.

          Maybe a smoothie upper for shot cartridges would make it the ultimate Alaska survival pistol…

      • My DE 50AE developed some issues in 2023, wasn’t fully returning to battery with Hornaday ammo. A gentle push on the back of the slide put it into battery. It happened around once every 5 rounds.
        Ran 200 rds of Armscor 50AE ammo without any issues back in December.
        Definitely something with the sizing of the Hornaday ammo.

        • I too have had the same problem with a .44 Mag DE. Sent it back to the factory and was told that a part was installed backwards (as in user error). Possible but not probable. It went in for a Cerakote job to a reputable gunsmith and had to be completely disassembled. Not sure if that was the culprit, but it came back running like a Singer sewing machine.

  2. Hey James! That’s very interesting. I know Hornady does some interesting stuff with some of their case lengths (for instance, Lee makes an entirely separate sizing die for their .45-70 Leverevolution rounds). My DE had almost the exact same problem, to the point I have brass shavings down the barrel after the last time I shot it (my nephew just turned 14 and wanted to show off for his Call of Duty video game buddies). It’s chambered in .44 Magnum, and I’m totally going to try some Armscor ammo I have to see if it’ll run that after I deep clean it.

    Thanks for sharing that story amigo! Hopefully I’ll find some success like you did. Have a wonderful night!

  3. cool gun but the 375GrizzinatorAR from Alaska Magnum ARs does a 260 grain bullet at 2650 fps. thats about 4000lbs of energy at the muzzle. It was designed to give 375 H&H mag performance in a semi-auto platform for grizzly bear hunting.

  4. Neat gun, on the low end I’d stick with 450 Bushmaster probably. The high end is extremely interesting in some niches though. In between them are rounds like 338 Federal and 358 Winchester. Probably better BCs and better availability of parts too. The other option would be something like a 300 win mag AR.

    The other thing about this is it’s certainly a reloaders gun. Yeah you may get some factory ammo here and there, but to really wring performance (much less being able to afford shooting it) from it you’re rolling ammo.


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