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The Modern Big Horn
As previously reported here at TFB, Big Horn Armory, the Cody, WY manufacturer better known for big bore leverguns has been working on an autoloading version of the venerable S&W .500 cartridge. The previous tentative moniker for this round was the .500 Auto Mag, but the round now has a final name of the .500 Auto Max. Buffalo bore currently has 4 factory loads ready to go for this rifle, with a few more being developed between the two companies. One of the initial loads, a .400gr HCFN, moves along at 2175 fps with 4200 ft.-lbs of energy at the muzzle. Big Horn Armory is beginning to complete rifles, and in anticipation of a 3/31/18 product launch, they are taking deposits on the guns as of today. Final price for the big-bore AR will be $1999. 
According to the president of Big Horn Armory, the .500 Auto Max can be considered a “functional twin” of .500 S&W, just in rimless form. As far as reloading goes, one “can use 500 S&W load data, dies and shellholders. It is a 60,000 psi cartridge that can achieve 4600 ft-lbs of muzzle energy.” A nice touch for this rifle and new cartridge is that brass for those who want to reload or create custom loads will be immediately available from Starline. A note for reloaders from Big Horn Armory:
The differences are the case and the method of headspacing. The 500 Auto Max headspaces on the mouth of the case, so you must use a taper crimp. DO NOT ROLL CRIMP THE 500 AUTO MAX! Trim to length 1.615″ is important for headspacing. The mouth end of the case should not be overhanging a bullet crimp groove.
This author also appreciates that due to the loads being developed and tested in conjunction with Buffalo Bore, one can be assured that stated velocities are being measured out of the barrel length the cartridge is intended for, not an ultra long proof-test rig. This author also remains firm in his hope that one day there will be a monstrous autoloading pistol chambered in this round, just for the the hell of it.
Press release per Buffalo Bore:
BIG HORN ARMORY ANNOUNCES THE AR500 IN .500 AUTO MAX
AR-style rifles are on fire in terms of popularity, so it is only natural to find out how much power can be stuffed into one. Big Horn Armory, maker of the semi-custom Models 89 and 90 lever-action rifles in calibers like .500 Smith & Wesson Magnum and .460 Smith & Wesson Magnum announced that it will be producing the AR500 chambered in a new cartridge, the .500 Auto Max. The AR500 is the most powerful AR-style rifle available in a big bore cartridge.
This rifle’s heart is an AR10/SR25-based receiver made from a forged 7075 aluminum in a more modern and stylized profile. The upper has been modified to provide reliable ejection of the .500 Auto Max cartridge cases, while the lower features ambidextrous bolt release, an ambidextrous safety, trigger finger rest and Ergo grip. An adjustable gas block allows the rifle to handle everything from sub-sonic loads to pachyderm slayers.
An 18-inch stainless steel barrel with a 1:24 twist and a threaded muzzle that has been black nitrided inside and out contains the beefy .500 Auto Max cartridge. It is free floated in an MLok hand guard with a full-length Picatinny rail on top and accessory points. The bolt carrier group has been modified to feed and extract consistently. A heavy-duty carbine buffer with an adjustable stock capped with a 1-inch recoil pad attenuates this powerful cartridge’s thump on the shooter. Most say it’s like shooting a .308 Winchester. The AR500 comes with a five-round magazine, but 10-rounders are also available.
Based upon the .500 Smith & Wesson Magnum cartridge, the .500 Auto Max is a rimless version of the parent cartridge. Factory ammo is available from Buffalo Bore with a 400-grain Hard Cast flat nose kicking out of the barrel at 2175 fps with 4200 ft.-lbs. of target thump. Brass for handloaders is available from Starline.
Orders are being accepted now at $1999.00 with an anticipated delivery of March 31, 2018. A $600 deposit is required to reserve a rifle.
For more information, please visit Big Horn Armory
