Best AR Calibers That Aren’t 5.56 NATO

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The AR rifle platform is a favorite for many American shooters because it’s incredibly versatile and available in a number of calibers useful for target shooting, home defense and hunting.

You can cover the spectrum with an AR, but that still begs the question: What’s the best AR caliber for your situation?

In this article we list the best AR calibers available in 2024, and why they work so well whether you’re looking to take an AR to the range, hunt, or defend your home.

If you can’t wait, the best AR caliber is a .22 Long Rifle. If you want to see the full AR caliber list, keep scrolling.

Our Top 3 AR-15 Caliber Picks

Here are our favorite AR-15 caliber choices:

  1. 22 Long Rifle - Best All-Around AR Caliber
  2. 6.8 SPC - Best AR-15 Caliber for Home Defense
  3. 6.5 Grendel - Best AR-15 Caliber for Long Range

Let’s examine each caliber in-depth, starting with our top pick, to help you choose the best AR caliber for your shooting needs.

22 Long Rifle - Best All Around AR Caliber

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 unquestionably the 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 starkly contrasts with converting your AR to other calibers, as these will require a new barrel.

AR-15 22LR conversion bolts and magazines are inexpensive, and 22 LR bulk ammo is dirt cheap and fun to shoot. You can easily spend an entire day firing 500 rounds of 22 LR for approximately 1/5 the cost of the same amount of bulk 5.56. This allows you to get a lot of training with your AR-15 without breaking the bank on ammo costs.

6.8 SPC - Best AR-15 Caliber for Home Defense

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, U.S. Special Operations Command (USSOCOM), 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 program’s goal was to mimic the stopping power of the 7.62x39mm Soviet round. In general, the 6.8 SPC was successful at accomplishing this task. But due to chamber design issues when Remington first presented their new round to the military, the 6.8 SPC was not adopted by the Armed Forces.

Even though the U.S. military passed on the 6.8 SPC, it isn’t ineffective. On the contrary, the 6.8 SPC is an especially potent short-range cartridge, boasting a 45% increase in kinetic energy compared to a standard 62 grain 5.56 NATO load.

This added kinetic energy makes the 6.8 SPC an excellent choice for your next home defense carbine. It is also a popular deer and hog hunting round within ranges up to 200 yards.

6.5 Grendel - Best AR-15 Caliber for Long-Range

The 6.5 Grendel is an excellent long-range cartridge for the AR-15, as it fires an aerodynamic 6.5mm bullet with a high ballistic coefficient and resultant 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 its long-range accuracy. Its 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 6.5 Grendel was conceived as an intermediate cartridge that would extend the effective range of AR-15 rifles out past 800 yards. Utilizing the 6.5 Creedmoor’s same higher ballistic coefficient 0.264” diameter bullets, 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.

6.5 Creedmoor - Most Accurate AR Caliber

If you don’t mind stepping up to a larger and heavier AR-10 rifle, then you can witness dramatically improved ballistic performance: precisely why competitive shooters often reach for the 6.5 Creedmoor.

The 6.5 Creedmoor is the cartridge that single-handedly started the 6.5mm love fest in North America. Introduced by Hornady in 2007, the 6.5 Creedmoor was co-developed by renowned marksman Dennis DeMille and Hornady senior ballistician Dave Emary. The two produced a cartridge that boasts low recoil, a flatter trajectory than the 308 Win, and relatively accessible 1,000-yard shots. 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 for a potent long-range target rifle.

Continue reading Best AR Calibers That Aren’t 5.56 NATO on Ammo.com!

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I would like to be captain obvious here for a minute. I realize no one here wrote that article about the best AR15 caliber but i feel it was seriously flawed.
Why title the article the best cartridge for the AR15 then mention the “best caliber” that is NOT EVEN AN AR15 cartridge? The author must think everyone is stupid and just a mouth piece for the creedmore cartridge. The 6.5 Creedmore does not even deserve mention in the article given it is not an AR15 cartridge.
Despite the 6.8 SPC being a good cartridge it has not taken off. The ammo is not easy to find so why mention it?
The 300 Blackout despite being intellectual stolen property by AAC (as the 300 Whisper) has been an excellent cartridge for over 45 years. With 125 grain bullets duplicates the AK47 and able to shoot 600 yards with ease. With 200-220 grain bullets the cartridge is a true suppressor cartridge. With 200-220 grain bullets the round is quiet, hard hitting, and accurate. It is readily available in most any gunshop that sells ammo and is easy to reload.
The round is such that it can be loaded with a wide variety of powders.
So since the 300 Blackout / 300 Whisper was not mentioned, i thought i would help the article out.

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Ammo.com does wear that badge

though I don’t know who’s posting???

If you read their team bio page they well deserve our patronage as more than just an ammo supplier.

Given the thoroughness of your reply I’d think they’d want to pay you for it and publish, well written and on target

To say a small .30 is the best pick?

I can’t argue, smaller rounds still keep the rifle light/manageable yet larger caliber hits harder :+1:

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I like my grendels.

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Shooterrex, i know several people that love that cartridge. A cowboy buddy of mine had me build a 6.5 grendal for his wife but he loves it too. She has shot deer and antelope with it. I have zero experience with it as far as shooting it but understand it is a great AR platform cartridge also.

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My 18 inch Grendel will repeatedly hit an oxygen cylinder at 700 yards.
I have a 22lr AR as well. The downside to these are the mags are pretty much all 10 rounds.

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I have 2 12" pistols and a 16" & 20" rifles. Ar platform but capability distance wise of the heaver 308. The pistols spend a lot of time in the golf cart running around the farm. Snapping turtles, yotes, and ground hogs dont survive the encounter.

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So what bullet and bullet weight do you shoot ? What is your velocity?

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I shoot Hornady Black 123gr ELD Match

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Iam out of town right now. my crono data is at home. I mostly shoot the Wolf100gr steel case. Federal 90gr TNT works well on yotes and ground hogs. The Hornady Black 123 gr shoots well and I’ve killed a few deer with it.

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Ok so this makes me very curious! Remember i am a gunsmith, i work in guns 5 or even 6 days a week. When i am not working on guns, i am talking about guns. I get phone calls as early as 0600 and as late as 2300 about guns.
So how many people shoot the 6.5 Grendal?
How many shoot the 300 Whisper / Blackout?
What other calibers are shot on the AR 15 platform.

So to let you know what i am looking for i did 4 tours in Iraq as a contractor. While the AR platform is not my first choice of weapons to grab i do keep two of them handy. I despise the 5.56 cartridge. It is too small a caliber having used it in combat . I had a rifle shot out of my hands during a firefight with an AK47, he actually shot me in the left thumb. The bullet went through my thumb, then the hand guard, the gas tube ripping the rifle out of my hands. I was given a modified and suppressed 300 blackout by a former Delta Force now contractor i was working with. I used that rifle till the day i was hit and medivaced out of Iraq. Shooting that was the shit for me as far as M4 platforms go. Hard hitting, accurate, but quiet. There are many bullets available for the 30 cal but with 125 grain it duplicates the AK 47 round with 200-220 grain they are pure perfection for suppressors.
So i have a M16 select fire in 300 BLKOUT with a 12.3” barrel and a titanium mono core suppressor of my own design. I shoot 200 grain subsonic rounds exclusively.
I also have a 9mm AR sub machine gun that takes glock mags. It has a 5.5” barrel with a titanium mono core suppressor of my own making. I shoot exclusively 147 grain subsonic rounds exclusively out of that.
So those are my choices for the AR platform. So again what rounds do you use? Why do you like them? Is the ammo readily available. With semi auto and machine guns i want ammo that is readily available by the case! Lever action rifles or revolvers i do not care about readily available ammo at all as i am loading for performance, obsolete or rare as in wildcat cartridges like my 41 Special.

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I own a couple of ARs but they are both in 5.56 . They are not what I reach for when I shoot for fun . Would not have them if it wasn’t for Hillary running for president in 2016 . I bought one before the election just in case and six months latter I won a Daniel Defense in a raffle . When I go hunting I always grab my Rem. 700 that I have used for 40 some years or a pump shotgun .

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For s select fire the 300BO or 9mm are good.
I dont run anything suppressed.
For long distance in an AR platform the 6.5 Grendel or the 6ARC are my pick. Ammo is available by the case online. I’ve even found some grendel locally. 6ARC is a grendel necked down to 6mm. Just a little better balasticly than the grendel.
I use the Grendel pistols around the farm for varmint control. One deer was also harvested with a grendel pistol because that is the gun that was available when the big doe stepped up to see what we were doing fixing a fence.
I use my AR10 type rifles in 308 or 6.5 Creedmoor for longer range shooting to 1000yds.
Past that I use my 300 win mag. My Bergara in 300 win mag has done a mile no problem.

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Old saying “Beware of the man who owns one gun! He probably knows how to use it.”
I use my M16 and 9mm submachine gun to advertise my short barrel rifles and for people to see how well my suppressors work. They are not my go to guns. I carry my 41 Special custom revolver and a 1892 lever action daily. I have several 870 pump shotguns around the house and the gunshop. So personally i like your choices.

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So you definitely like the AR platform. A good platform easy to modify / customize!
I must say you are educating me and causing me to look at other calibers. I get asked about other calibers for the AR15 quite often but i have never looked into them. So thank you for giving me some of your experience with them. Much appreciated

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I have a few different calibers, 458 SOCOM, 25-45, some 308’s, some 5.56. All good shooters. Think I like the 308’s the best. Something about the Ka-Chung of a 308 cycling just seems right.

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I have ARs in 10 different caliber. I have from 17 HMR up to 450 Bushmaster. If ease of ammo acquisition were of no concern, I would keep my 6.5 Grendel. It is very accurate and has a good amount of force at long distance. For a fun, albeit more expensive than necessary, round to shoot targets or small game out to 3-400 yards, I like my AR57.

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I wrote an article about caliber swapping in 2017. Swapping AR uppers, 1 gun multiple purposes | The 22 Man
I love the 300 blackout. 6.8 was good, my 6.5 Grendel was a disappointment CBC Industries 6.5 Grendel Review | The 22 Man however I got the new barrel installed during Independence Weekend so it may turn out better.
9mm is a fun plinker and for IDPA, USPSA, Steel challenge.

I do have to admit, several people shooting the 5.56 in 77grain overseas have been very fond of what it does. However, most of those that could used AK’s over “there”.

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I will take the time to post a picture of my model 14r Remington. It was my grandfathers deer rifle in New York .

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I used an AK47 when not working with other troops. When working with other troops you do not want to sound like the enemy. When working with other units or major operations like the first and second invasions of Fallujah is when i used a suppressed 556 then 300 BLK OUT.

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