Five AR-15 Calibers for Hunting Deer [Updated Guide]
8/31/2018Primary Arms Staff7/6/2020 1:22 pmwww.primaryarms.com
Five AR-15 Calibers For Hunting Deer [UPDATED GUIDE]:
AR-15 and AR-10 style rifles have encroached on the territory that was once only occupied by wooden-stocked bolt and lever guns. It's not hard to decipher why, the modern sporting rifle is the most popular rifle in the nation, and shooters want to be able to put them to use on the hunt. As the popularity of the platform has increased, so has the demand for powerful new cartridges that provide shooters with the performance needed to drop deer using their black rifles. Today, we are breaking down five AR-15 and AR-308 calibers -- one in each caliber class -- that will help you bag that buck whether you're sitting in a tree stand shooting short shots down narrow lanes, perched in a blind looking out over acres and acres of flat land and fields, or stalking muleys over hill and dale. Which one will be responsible for packing your freezer and hanging a big fella on the buck pole this fall? Let's dive in.
The 6.5 Grendel cartridge was designed in part by Bill Alexander of Alexander Arms, and the goal of the project was to create a round for the AR-15 that had a superior ballistic coefficient and terminal performance than .223 Remington or 5.56 NATO. Grendel projectiles can be up to twice as heavy as standard 5.56 NATO rounds, and can reach velocities of around 2500 fps, all while shooting relatively softly for the power it’s packing. The 6.5mm bullet is long and thin, giving it excellent wind bucking abilities that can deliver a punch with almost double the kinetic energy than a .30-30 at 300 yards. Much beyond that distance, terminal energy begins to drop below 1000 foot-pounds, and the effective range – and ethical comfort level – of many hunters is starting to peter out as well. If you’re the guy or gal in a blind or tree stand, chances are good the Grendel will fit your needs and do so very well.
There are some things to consider if you choose 6.5 Grendel as your new deer hunting round, primarily the fact that 6.5 Grendel comes in two flavors: Type I and Type II. As you might have guessed, components that work with one type are potentially dangerous to mix with use of the other type. The good news is, Type II has become the most widely used version, and is more than likely what most people are referring to when they say “6.5 Grendel.” But it is still vitally important to be sure you’re working with the parts and ammunition you’re intending to when building or buying a rifle chambered for this cartridge. If you’re looking to convert a .223 Remington or 5.56 NATO AR-15 into a 6.5 Grendel deer rifle, all you need is a new bolt carrier group, a barrel, and some 6.5 Grendel magazines. A popular choice for many shooters that hunt with their ARs is to build a dedicated 6.5 Grendel upper and swap that out for their standard .223/5.56 upper when deer season comes around. The modularity of the modern sporting rifle makes it easy and convenient to quickly turn the one rifle you already have into two.
.300 AAC Blackout
The .300 Blackout cartridge has grown wildly in popularity since it hit the shelves in 2011. Like the 6.5 Grendel, the .300 BLK was designed to fit a specific need for the U.S. Military. Blackout was designed to maximize the performance of a suppressed carbine rifle. Advanced Armament Corporation started with the .300 Whisper wildcat cartridge and made some minor modifications, allowing the round to fit, double stacked, in magazines designed for .223 Remington or 5.56 NATO cartridges. To accomplish what the military was looking for, .300 BLK used 220 grain bullets for subsonic performance that could be suppressed with great effectiveness. But the lighter weight supersonic loadings also worked incredibly well, reaching speeds of around 2200 feet per second with 125-130 grain bullets. It’s not a round that’s going to break any speed records, but a 30-caliber bullet from an AR-15 rifle is something that the public took to with significant swiftness.
The Blackout has a lot going for it, but it has limitations as well. The .300 BLK casing is essentially the same dimensions as .223 Remington brass, trimmed down and necked to accept the 30-caliber bullet. This means considerably less room for powder. Blackout burns through its propellant in about roughly a 10-inch barrel, which makes it popular for the SBR and AR Pistol crowd, but it also means it loses velocity much faster than other 30-caliber cartridges. Because of this, you’re going to be limited to much shorter ranges to be effective enough to hunt deer. Now, if you’re the hunter up in the hardwood forests sitting in a tree stand or a ground blind where the vast majority of shots taken are under 75 yards, you’ve got nothing to worry about. In fact, I would dare to say you’re in luck. The supersonic loadings that many manufacturers are offering in .300 BLK pack a serious punch. Moving faster than their subsonic, suppressor-friendly counterparts, quality .300 BLK hunting ammunition like the Barnes VOR-TX 110 grain round can expand to twice the diameter of the bullet upon impact. This creates a more intrusive wound channel than a .223 ever could, and effectively and ethically puts down deer-sized game. While the heavier weights of subsonic loads might seem advantageous for taking game to some, in .300 Blackout these rounds are just moving too slow to expand enough and be reliably lethal.
The number one advantage of the 300 Blackout is how versatile it makes the AR-15 platform. All that is required to take your AR-15 from a .223/5.56 plinker to a deer-dropping hunting rifle is a .300 Blackout barrel. Blackout uses the same bolt, same magazines, and same lower receiver as your standard MIL SPEC AR-15. Just like with Grendel, a popular way to turn one rifle into two is to just build a dedicated 300 Blackout upper and swap it on when you want to hit the range to shoot suppressed subsonic rounds or sit in the woods with supersonic buck-slayers.
First idealized in concept by Lt. Col. Jeff Cooper, whose contributions to the firearms community are hard to overstate, the “thumper” concept lives on today in a small handful of calibers for the AR-15 platform. One such caliber is the .450 Bushmaster, and we think it makes for a fantastic deer hunting rifle. Cooper’s dreams of a “thumper” came with some stipulations. Whatever type of rifle was going to fit the Thumper concept had to be big bore, so .44-caliber or larger. He also envisioned it being semi-automatic, lightweight, and capable of one-shot takedowns on large game at 250 yards and closer. Bushmaster Firearms was given the license to Tim LeGendre’s “.45 Professional” cartridge and, working with Hornady, made some slight modifications to the round turning it into the .450 Bushmaster.
It’s not difficult to understand the potential benefits of a big bore caliber in an AR-15, and Bushmaster packs the hard-hitting performance to boot. High quality factory loadings from leading ammunition manufacturers can attain muzzle velocities around 2200 fps with a 250-grain bullet that’s still packing 1250+ foot/pounds of energy at 200 yards. That’s a lot of thump. A significant benefit of the Bushmaster over the other limited number of big bore options for the AR-15 is the fact that it uses a straight-walled casing. In many regions around the country, hunting in “limited firearm zones” means there are strict rules about the types of ammo you can use to hunt deer. In my home state of Michigan, as an example, the southeastern region of the state was once restricted to shotguns and muzzleloaders only. In 2014, the regulations were changed to include .35-caliber or larger straight-walled cartridges with a case length between 1.16 and 1.80 inches. This still eliminated popular big bore options like .45-70 Government lever action rifles but leaves the door open for cartridges like .450 Bushmaster, which deliver similar performance at appropriate ranges and can be fired from the AR you already have with dedicated .450 upper receiver. To equip your AR-15 to shoot .450 Bushmaster, the bare essentials you will need are a .450 bolt, and a .450 Bushmaster barrel. It’s also likely that you’ll need to have your upper’s ejection port opened up a small amount. We suggest having a gunsmith do that for you unless you’re very experienced with gunsmithing yourself. As with the previous calibers, many shooters will build a dedicated upper receiver to swap onto their lower when it’s time to hunt
The limitations of the cartridge are also obvious. In a short action rifle with the size limitations of the AR-15, pushing a 250-grain projectile with any considerable speed is nothing short of a feat of engineering. But the Bushmaster’s ballistic coefficient does mean that when the round starts slowing down, it slows down fast. While many loadings today carry enough energy to ethically take a deer at 300 yards with .450 Bushmaster, the bullet will have dropped somewhere in the neighborhood of 40 inches at that distance. Again, the number of hunters taking those shots is miniscule compared to the number of hunters taking shots at 100 yards or less, so the odds are good that you’re not worried, but it is still worth noting. Bushmaster is also the cheapest big bore AR-15 round to shoot, running you about a buck-fifty for hunting ammo. That’s anywhere from $1.00 to $1.50 per round cheaper than the other popular big bore cartridges, .458 SOCOM and .50 Beowulf. For those reasons, we included Bushmaster on this list. For all of you out there that want to see a breakdown of these three big bore options head-to-head, stay tuned.
The granddaddy of them all. Arguably the most popular short-action hunting cartridge for large game in the world, and for good reason, the .308 Winchester has stood the test of time. Not much has to be said about the .308’s effectiveness on the hunt – it’s got over half-a-century’s worth of trophies on the buck pole to evidence its point. It’s also been the parent case to many cartridges that have seen success for shooters and hunters alike over the decades, such as the .243 Winchester and the venerable 7.62X51mm NATO. It is a cartridge based on the older .300 Savage and designed for semi-automatic effectiveness, supplanting the .30-06 in en-bloc magazines used by American servicemen carrying the M1 Garand during WWII.
The .308 has certainly got history on its side, and it is growing again in popularity due to the commercial success of DPMS pattern AR-10 style rifles. With a longer chamber, larger bolt head, and all the modularity and versatility of a modern sporting rifle platform, the AR-10 has become a hunter’s dream. The .308 Winchester pushes the modern sporting rifle’s capabilities well beyond the limits of the smaller calibers of the AR-15. Factory loadings for the .308 Winchester range in weight from 125-grain all the way up to 220-grain subsonic loads. The cartridge’s popularity also means plenty of information and hardware is easily accessible for hand-loaders who want custom-tailored, high-performance loadings that really push the limits of the Winchester’s capabilities. From the factory, a match grade 168-grain load will pack more than 1000 foot-pounds of energy out to about 600 yards or so out of a 24” barrel. That’s well beyond the limits of any AR-15 hunting cartridge. So, if you’re the hunter out on the plains or up in high country who may need to be ready for a long shot if that’s all you’re given, consider stepping up to the AR-308.
The .308 Winchester is a lot like the grizzled elder who’s still running with the young men in a profession where men die young. Many have tried to challenge the Winchester over the half-century since its introduction, but it has long seemed as though those challengers would inevitably rise in hype and popularity only to fall again into relative obscurity – only mentioned in the whispers of a dwindling few on forgotten forum boards scattered across the internet. But to believe, with all our technological advancements since the mid-1950s, that no real contender would ever rise up and place itself squarely into the same arena as the .308 would be foolish. It was only a matter of time, and that time may well have come…
The 6.5 Creedmoor was born not of wartime necessity, but from the dreams of long distance shooter Dennis DeMille, and the ballistics knowledge of Dave Emary, senior ballistician at Hornady Manufacturing. DeMille, a high-power rifle shooting champion, was lamenting the inefficiencies of commonly available high-power ammunition and his reservations with hand-loaded wildcat cartridges that were becoming so widely used among high-power, long distance competition shooters. The Creedmoor was purpose built to be so excellent at what it was designed to do that it would achieve wide adoption among these competitors and level the playing field. Shooter’s precision marksmanship skills would be the determining factor in competition, not the capability of their hand-loaded wildcats. The 6.5mm bullet was chosen because it’s proven to be one of the most ballistically efficient projectiles available due to its high sectional density. The casing is based on the .30 Thompson Center cartridge, which was itself based on the .308 Winchester. So, you could say with some degree of accuracy that the Winchester is quite literally the granddaddy of 6.5 CM. If nothing else, Creedmoor certainly stands on its shoulders.
Creedmoor took off with long-range competition shooters in the late 2000s. Within a few years, however, hunters started to take note as well. Creedmoor outperforms .308 in all but a few categories. The Winchester has a higher initial velocity – from the muzzle out to about 100 yards – and more energy until about 300 yards, at which point the more efficient 6.5mm bullet retains energy significantly better at subsequent ranges. But the real benefit of the Creedmoor is how flat it shoots and how well it bucks the wind out to the longest of ranges. In a 10-mph full value cross wind at 500 yards, the .308 Winchester has been pushed about 6 inches further off target than the Creedmoor. Out to a thousand yards, that difference is more in the neighborhood of 45-50 inches. For the long-distance hunter, or the hunter who just wants a fast, flat-shooting cartridge for their AR-10, the Creedmoor shines.
You can hunt and take trophy 12-points with your AR -- here's proof.
Buck Buchanan, of 'Just Killin' Time' on the Hunt Channel and Pursuit Channel.
Which Hunting Caliber Is For You?
Hopefully you have seen from this article that only you can truly determine what will be dropping deer for you this fall. Make no mistake, all of the hunting rounds discussed here today will get the job done – and there are more still that reliably harvest deer for hunters every year. It’d be close to impossible to compile a complete list of every bullet that has ever hung a buck on the pole. But these are proven solutions that make the most out of the adaptable and versatile platform of the modern sporting rifle, and if you’re looking to hunt deer this year with your favorite AR then you cannot go wrong with any of these choices. We wish nothing but safety and the best of luck to all the hunters out there who will be putting meat on their family’s table and trophies on their walls this fall. Have a great hunting season.
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