Let’s be honest about one thing, the 5.56 NATO/223 Remington is a battle-proven cartridge that has valiantly served the US military for decades. The 5.56’s effectiveness is well documented, and it is one of, if not the, most popular centerfire rifle cartridges in North America.
Yes, the 5.56 NATO is awesome. It has low recoil, a flat trajectory, is inexpensive, and has more varieties of ammo than you can shake a boomstick at.
But sometimes you want to shoot something different out of your AR, and that’s ok. One of the greatest aspects of the AR-15 rifle is its versatility, as many caliber conversions can be accomplished with a simple upper receiver swap. However, with so many different rifle calibers available, some shooters might be confused as to which cartridge is best for their AR-15 or AR-10.
In this article, we are going to break down the top 13 best AR calibers that aren’t 5.56 NATO so you can understand which one will best suit your shooting needs.
If you can’t wait, the best AR caliber is .22 Long Rifle, however if you want to see the full AR caliber list then keep scrolling.
If you’re like me, the first shot you ever took was with a 22 Long Rifle. As the most popular round on the planet, the 22 Long Rifle is the unquestionable best AR caliber thanks to its nonexistent recoil, extremely low cost, and high ammo availability.
The greatest benefit of the .22 Long Rifle (or 22 LR for short) in an AR-15 platform is that it allows you to train with your standard 5.56 NATO rifle for a fraction of the cost. Converting an AR-15 to 22 LR only requires a conversion bolt and new magazines as any AR 5.56 barrel can be used for 22 LR.
This is in stark contrast to converting your AR to different calibers as these will require a new barrel.
AR-15 22LR conversion bolts and magazines are inexpensive and of course 22 LR bulk ammo is dirt cheap and fun to shoot. You can easily spend an entire day shooting off 500 rounds of 22LR for approximately 1/5 the cost for same round count of 5.56.
This allows you to get in tons of training with your AR-15 while not breaking the bank in ammo cost.
If you’re looking to build or buy an AR pistol and want a cartridge that delivers optimal performance in a short barrel length, look no further than the 300 Blackout.
Developed in 2010 by Robert Silvers and the Advanced Armament Corporation (which was later acquired by Remington), the 300 Blackout increases the caliber of the AR-15 rifle to 0.308” while maintaining standard NATO mags. To put it simply, the 300 BLK is a 5.56 case that has the case mouth widened to accept a 30-cal bullet.
This allows the 300 BLK to fit in standard AR mags and maintain their normal 30-round capacity. It also means that you do not need to purchase a new bolt to fire 300 Blackout, as the base diameter of the case is unchanged from 5.56. Although the mags and bolt remain unchanged from a standard AR-15, a new barrel is required to perform a conversion.
The 300 Blackout was designed to experience a full powder burn in a 9-inch barrel, meaning it works extremely well when used in a short-barreled rifle (SBR) or AR pistol. The 300 BLK is available in supersonic and subsonic factory loads, making it an extremely versatile round. Supersonic loads work well for target shooting, long range engagements, and whitetail hunting while subsonic rounds are ideal for use with a suppressor.
The 6.8 SPC makes an excellent choice for home defense as it was developed specifically for indoor combat and has exceptional short range terminal ballistics.
Developed in 2004 as a joint operation between Remington Arms, US Special Operations Command (USCOCOM), and the U.S. Army Marksmanship unit, the 6.8 Special Purpose Cartridge (SPC) was designed to increase the terminal performance of the M4 carbine.
The goal of the program was to mimic the stopping power of the 7.62x39mm Soviet round, and in general the 6.8 SPC was successful at accomplishing this task. Sadly, due to chamber design issues, the 6.8 SPC was not picked up by the armed forces for combat use.
Even though the US military dropped the 6.8 SPC, this doesn’t mean it isn’t an effective round. On the contrary, the 6.8 SPC is an incredibly deadly short-range cartridge, boasting a 45% increase in kinetic energy compared to a standard 62 grain 5.56 NATO round.
This added kinetic energy makes the 6.8 SPC an excellent choice for your next home defense carbine and is also popular as a deer and hog hunting round for shots under 200 yards.
The 6.5 Grendel makes an excellent long-range cartridge for the AR-15 as it fires an aerodynamic 6.5mm bullet that has a high ballistic coefficient and flat trajectory.
Although it took a little while for the 6.5mm bullet to take hold here in North America, long distance shooters have become keenly aware of the effectiveness of a 6.5 for long range accuracy. Their incredibly sleek and aerodynamic design makes for a high speed/low drag projectile that is ideal for long range target shooting.
Developed in 2003 by Alexander Arms, the goal of the 6.5 Grendel was to develop an intermediate cartridge that extended the effective range of AR-15 rifles out past 800 yards. Utilizing the same higher ballistic coefficient 0.264” diameter bullets used by the 6.5 Creedmoor, the 6.5 Grendel can maintain MOA-level accuracy and supersonic velocities out to 1,200 yards with half the recoil of the 308 Winchester.
The 22 Nosler makes an amazing choice for varmint hunting due to its high velocity, flat trajectory, and lower recoil compared to other intermediate cartridges.
Ever wonder what it would be like to get 22-250 Remington velocities in a standard AR-15? The 22 Nosler nearly accomplishes this thanks to a 25% increase in case capacity when compared to 5.56 NATO. This capacity increase leads to 14% higher muzzle velocity and a 30% increase in kinetic energy according to Nosler’s website.
Although you’ll need a new barrel for the 22 Nosler, the standard AR-15 bolt will work for the Nosler round as the cartridge uses a rebated rim.
Debuted at SHOT Show 2017, the 22 Nosler was the fastest AR-15 cartridge of its time boasting velocities normally reserved for bolt action calibers like the 220 Swift and 22-250 Rem. To put this into perspective, a 22 Nosler can launch a 55-grain projectile at 3,500 fps compared to 3,680 fps for a 22-250.
For varmint hunting, lightweight projectiles with high muzzle velocity are preferred, and the 22 Nosler delivers this in spades.
The 224 Valkyrie is one of the best 22-caliber long range cartridges because it was designed to shoot heavier 0.224” diameter bullets than a 5.56 NATO cartridge can handle.
One of the main drawbacks of the 5.56 NATO is that the longest bullet that can be seated to proper magazine length is 77 grains. These bullets are great for medium range shots, but if you want to shoot longer distances, you’d prefer to have something like a 90 grain Sierra Matchking (SMK for short).
Federal Premium Ammunition took note of the release of the 22 Nosler at SHOT Show 2017. Not wanting to be outdone, they went back to the ballistics lab and designed a cartridge that would directly compete with the 22 Nosler.
Instead of using a proprietary case design like the 22 Nosler, the 224 Valkyrie uses a necked down 6.8 SPC case to accept a 0.224” diameter bullet. The resulting cartridge allowed for the use of the 90 gr SMK in a standard 6.8 SPC magazine.
Federal released the 224 Valkyrie at SHOT Show 2018 the following year topped with a 90 gr SMK that has a ridiculously high BC of 0.563. This high BC allows the 224 Valkyrie to shoot upwards of 1,300 yards, affording long range shooting competitors an incredibly low recoiling, economic cartridge that can achieve sub-MOA accuracy in a sport often dominated by larger calibers.
If you enjoy long range target shooting and want to stick with a 22-caliber bullet, then the 224 Valkyrie is unquestionably the best choice.
A relative newcomer from Hornady to the shooting scene, the 6mm ARC cartridge fires a 0.243” diameter bullet that has proven to be effective against varmints, antelope, coyotes, and whitetail deer. It covers a wide breadth and depth of hunting capabilities which makes it the best multipurpose hunting cartridge on the market for the AR-15.
The 6mm Advanced Rifle Cartridge (ARC) was introduced by Hornady Ammunition in 2020 and is the youngest round on our top 13 list. It was developed at the behest of the United States Department of Defense (DoD) for its multipurpose combat rifle program.
Designed by necking down a 6.5 Grendel case to accept a 6mm bullet, the 6mm ARC requires a bolt, barrel, and new magazines to perform a conversion from a standard AR-15. The 6mm ARC provides shooters with improved ballistics over the 6.5 Grendel, mostly due to its higher muzzle velocity.
Capable of launching a 103 gr Hornady ELD-X at 2,800 fps with 1,792 ft-lbs of kinetic energy, the 6mm ARC is a flat shooting, hard hitting round that is more than capable of dispatching virtually any varmint that plagues your property shy of bears and elk. Ground hogs, coyotes, and deer stand no chance against this hotrod, making it a jack-of-all-trades hunting cartridge that mimics the 243 Winchester in a semi-auto platform.
If you don’t mind stepping up to a larger and heavier AR-10 rifle, the amount of ballistic performance you can achieve increases dramatically. And when it comes to ballistic performance for long range shooting, competitive shooters often reach for the 6.5 Creedmoor.
The 6.5 Creedmoor is the cartridge that single-handedly started the 6.5mm cartridge love fest in North America. Introduced in 2007 by Hornady Ammunition, the 6.5 Creedmoor was the product of a gripe session between legendary shooter Dennis DeMille and Dave Emary, the senior ballistician of Hornady at the time.
What they produced was a cartridge that was low recoil, had a flatter trajectory than a 308 Winchester, and was capable of making 1,000 yard shots with relative ease. Extremely tight tolerances in the chamber throat design make the Creedmoor one of the most inherently accurate out of the box rounds available in the market today.
Combining the accuracy and lower recoil of the 6.5 Creedmoor with the semi-automatic capability of the AR-10 makes a potent long-range target rifle.
The tried-and-true 308 Winchester and the namesake of the AR-10 is one of the best big game hunting cartridges for the AR-10 as it can take down whitetail, black bear, and elk with relative ease.
Developed in the 1950’s to replace the aging 30-06 Springfield, the 308 Winchester has been the go-to round for designated marksmen, snipers, and machine gunners since its release. The 308 Win has also cut its teeth in the back woods and is the favored big game hunting cartridge for many outdoorsmen.
With seemingly unending bullet and load variations, there is a 308 Win for every possible hunting scenario and it gets the nod for our best big game hunting cartridge for an AR-10 rifle.
If you like performing mag dumps, shooting high volume without breaking the bank, and having a carbine with virtually zero recoil, then a 9mm Luger pistol caliber carbine might be in your future.
The pistol caliber carbine (PCC) is becoming more popular in the AR-15 community as handgun rounds are generally less expensive than centerfire rifle ammo.
The PCC is becoming so popular that there are now lower receivers that are specifically produced to accept Glock magazines instead of standard sized AR mags. And let me tell you something, there’s nothing quite like dropping 33 rounds of 9mm in about 5 seconds out of a Glock stick magazine!
For afternoons of unending plinking fun, you simply can’t beat the cost per round of the 9mm Luger.
An AR pistol with a shorter barrel length would also make a fine home defense weapon, allowing for lightning-quick follow up shots, a more stable shooting platform than a handgun, and extremely high magazine capacity.
AR pistols are also often chambered in 40 S&W and 45 ACP, but the 9mm Luger cannot be beat for cost-effectiveness and recoil.
If you’d like to learn more about how the 9mm compares to the 40 S&W and 45 ACP then check out this article: 9mm vs 40 S&W vs 45 ACP.
If you want to go deer hunting in North America and plan to use an AR-15, you cannot beat the stopping power, range, and bullet selection of the 450 Bushmaster.
Now we come to the Thumper Rounds as coined by the late and great Best AR Caliber for Hog Hunting
The 458 SOCOM is another thumper round that makes an excellent hog hunting cartridge thanks to its ridiculously high muzzle energy and fast follow-up shot capability.
There’s no denying that the 458 has made a name for itself with whitetail hunters and elk enthusiasts alike, but hog hunting is where the 458 really shines.
The ability to take fast follow-up shots with a hard hitting round like the 458 makes it perfect for engaging multiple targets or making seconds shots on tough game like hogs. Feral pigs have become an increasingly large problem in the southern United States, as a herd of hogs can destroy an entire field in a single night.
Ammo availability is the one of the few downsides to the 458 SOCOM, since it is not SAAMI certified only custom ammo manufacturers currently have ammo for the cartridge. However, if you handload this can easily remedy the ammo situation as multiple bullet manufacturers have special bullets available for the 458 SOCOM such as the 300 grain Barnes TTSX hunting bullet.
Like the 450 Bushmaster, performing a 458 SOCOM conversion requires a new bolt, barrel, and single-stack magazine follower. The bottle-neck design of the 458 SOCOM lends itself to more reliable feeding and higher case capacity than straight-walled cartridge designs of similar size.
In a self-defense situation, the 458 SOCOM would make an excellent choice. However close range shots could result in overpenetration, so properly expanding bullets would be a must if you plan to employ the 458 for this purpose.
Despite difficulties in locating factory ammunition, the 458 SOCOM is an incredibly powerful cartridge that is excellent for slaying feral pigs in rapid fashion.
We saved the biggest for last, as the 50 Beowulf fires the heaviest and widest projectiles in our top 13 best AR cartridges list. Developed for checkpoint security and firing through automotive glass, the 50 Beowulf is a powerful 50-caliber round that delivers magnum-level terminal performance in the compact and lightweight AR-15 platform.
The 50 Beowulf is the second cartridge from Alexander Arms on our top 13 with the 6.5 Grendel being the first. Designed using an elongated rebated rim 50 Action Express (50 AE) case, the 50 Beowulf looks to bring 50-cal power to the AR platform by firing massive 300 to 400 grain bullets that are not easily deflected by auto glass or vehicle body panels.
To put this into perspective, the 50 Beowulf has similar ballistic properties as black powder versions of the 45-70 Government, which was one of the rounds that nearly led to the extinction of the American Buffalo.
A lot of focus has been placed on the 50 Beowulf for its tactical applications, however it has also become an incredibly effective sporting round for close range shots on whitetail under 150 yards.
Like the 458 SOCOM, ammo can be scarce for the 50 Beowulf as Alexander Arms is the primary manufacturer. However, reloading can really help alleviate this restriction and allow you to customize your 50 Beowulf ammo to your specific shooting needs.
If you’re looking for a big bore AR-15 rifle cartridge that is exceptional at close range engagements, you simply cannot go wrong with the 50 Beowulf!
If there’s one word that describes the AR platform, it must be “versatility”. With so many different accessories like handguards, grips, triggers, and sights, you can customize your AR to whatever you want it to be.
The same is true for chamberings, as there are so many different calibers that have been successfully adapted to the AR-15 and AR-10 rifles that each have their own pros and cons. No matter what plans you have for your new AR, selecting the best AR caliber is now a bit easier thanks to our top 13 list.
If you need ammo for any of these calibers, make sure to check out the wide variety of ammo in stock here at Ammo.com, as we strive to always bring you the best prices on the Internet. If you want to save even more, consider our numerous bulk ammo options available now and we will see you out on the range!
The Top 13 Best AR Calibers That Aren’t 5.56 NATO originally appeared in The Resistance Library at Ammo.com.
