There are two black guns used as hunting rifles. The AR-15 (technically Colt owns the rights to the name, but it has become a generic moniker for the design) is the most common and is designed around the .223 Remington-size cartridge. The AR-10 (again, ArmaLite owns the rights to the name) is bigger and is designed around the .308 Winchester. Both are kicking butt in the hunting world right now, but this article looks at the smaller, lighter and much more popular AR-15 platform and the cartridges used. The following is not all of them, just the most popular. If you care to look, you can find guns chambered in such diverse cartridges as the .17 rimfire or the .50 BMG.
.204 Ruger The .204 Ruger is a great match for an AR-15. Advertised as the fastest current production rifle cartridge, it is a good choice for prairie dog shooting and predator hunting. The .204 is accurate, has a flat trajectory and produces low recoil. My personal .204 Ruger is an upper I built myself. With ammo it really likes, it will shoot quarter-inch, five-shot groups. The flat trajectory and high velocity are well suited for long-range work if the wind is not too stiff. The low recoil helps keep the target in the scope so the shooter can see the impact.Hornady lists its 32-grain load with a muzzle velocity of 4225 fps, the fastest factory load of any cartridge on the market. The .204 Ruger is also available in 40-grain and 45-grain loads, which are a better choice for hunting coyotes.
.223 Remington (5.56x45 NATO) Without a doubt, and by a very wide margin, the .223 Remington is the most popular cartridge available in AR-15s. It is also one of the top-selling rifle cartridges on the market, so there is a huge diversity of ammo and bullet options. The best hunting bullets will be from 40 grains through 55 grains, although Steve Johnson from Hornady loves the 75-grain BTHP and tells me it is the best coyote stopper he has used in this cartridge. Maybe, but it will take a lot for me to give up the Hornady 55-grain V-Max for my coyote hunting. At the risk of all the letters from Texas that are guaranteed every time I write this, I will state here again that in my opinion the .223 Remington is not ideal for deer hunting.
.243 WSSM This cartridge might be the ultimate dual-use AR-15 hunting round. With a 55-grain bullet at 4060 fps, it is a varmint- and predator-hunting machine. Then turn loose a 100-grain at 3110 fps and it’s a death ray for deer and antelope.
6.5 Grendel Bill Alexander of Alexander Arms started his company with the idea of hunting with ARs before hunting with ARs was cool. This was one of the first two cartridges he introduced. It has a big following for long-range tactical work, but Bill was thinking about hunters when he made it. The 6.5 Grendel started as a proprietary cartridge for Alexander Arms, but it has been picked up by several other manufacturers, including Les Baer.
6.8 Remington SPC This .270-caliber cartridge started life as a fighting round designed by some Special Forces types to bring more power to the AR-15.Its future as a military round is not looking good, but it has become popular with civilian AR-15 shooters. It’s another cross-over cartridge, suitable for predators and smaller big game. I have used the 6.8 SPC to take several whitetails and a mountain lion. With the right bullets it works fine.
.30 Remington AR This brand-new cartridge was introduced by Remington at the 2009 SHOT Show. It is engineered for deer hunting with the company’s R-15. The cartridge is a necked-down .450 Bushmaster and it has an advertised muzzle velocity of 2800 fps with a 125-grain bullet. My 20-inch DPMS rifle averaged 2685 fps for the two different Remington loads tested. With the 125-grain CoreLokt ammo it shot five, five-shot groups that averaged less than an inch.
.450 Bushmaster This big-bore cartridge is made for close-range big-game hunting. It pushes a 250-grain Hornady bullet out the muzzle at 2200 fps. That duplicates the three-pellet, 150-grain magnum muzzleloader performance well-proven on deer and other big game; in fact, it is the same bullet Hornady sells for muzzleloading.
.458 Socom This is another cartridge with a military birth. Rock River Arms offers the guns and Corbon has ammo. This rebated rim cartridge pushes a 300-grain bullet to 1900 fps, which duplicates a modern .45-70 load.
.50 Beowulf The Beowulf is another of Bill Alexander’s cartridges. It’s a big case with a severely rebated rim so it fits well in the AR-15 bolt face. The cartridge delivers a 325-grain bullet out of a 24-inch barrel at 2010 fps.This is a whole lot of bludgeon in an AR-15, and it has been my cartridge of choice for hunting big game in the thick stuff with an AR. I have had mine for years and can attest that it hits any target very hard.