5 Best AR-15 Calibers and Cartridges for the Money [2019 Review]

The AR-15 is one of the most versatile rifles that money can buy. Its standard 5.56x45mm cartridge is in use worldwide by police and NATO forces, so you know it’s good.

Lately, it seems a popular thing in the gun world to knock the 5.56. But mostly that’s just because people want something new, even if they don’t really need something new.

So, maybe you’re looking for a bigger caliber, something with a little more bang than the 5.56 (pun intended). Never fear, there are some options for you to consider. The most common of these more powerful cartridges are:

 ProductPriceWhere To Buy
image of .300 AAC Blackout
.300 AAC Blackout
image of 6.5 Grendel
6.5 Grendel
image of 6.8 SPC
6.8 SPC
image of .458 SOCOM
.458 SOCOM
image of .50 Beowulf
.50 Beowulf

Of course, with each of these alternatives, you’ll discover there are both advantages and disadvantages.

What to Consider When Seeking an Alternative AR-15 Caliber

Making the choice to upgrade your AR has consequences and can affect lives in the real world.

It can make you look like an idiot, never mind the damage to your bank account, if you don’t choose the right caliber for the job.

But, what’s the difference between the different cartridges for the AR-15?

There are three basic categories to think about when choosing a cartridge for your AR and these three usually involve some compromises between power, cost, and usefulness.

You should also consider flexibility and availability of rounds (the 5.56, being the most common cartridge, is readily available).


Everyone knows bigger cartridges are more powerful, right? Not necessarily.

The power of a cartridge depends upon two main factors: velocity and penetration. Though these factors are different, they’re still similar, and one affects the other.

Think of velocity like the engine of a car. It’s what gives the bullet the ability to move. Velocity is defined as: “an object is the rate of change of its position with respect to a frame of reference. Velocity is equivalent to the specification of an object’s speed and direction of motion.

Consider these velocities and weights.

image comparing the different velocities of objects

Yeah, I’m not getting math involved here, though velocity can accompany some scary mathematical equations. If you’re into math, you can research numbers like the kinetic energy of a round. If you’re not, suffice it to say that velocity means motion: the bullet moving through the gap between you and a target.

Bullet weight (also called grain or gr, is a unit of measurement) is the ‘transmission’ of the car engine; it’s what gives the round the ability to move (achieve velocity). This is what causes round penetration, and for both hunting or defense, maximum penetration should be your main thought.

Why do these factors matter?

Well, light bullets at high velocities will still lack the penetration of heavier bullets moving at medium velocities. The weight gives the bullet its capability to penetrate the target.

Think of it like this: you wouldn’t drive a semi to work every day, nor would you hook up a sub-compact car to a trailer to haul it. Your power-to-weight ration wouldn’t be sufficient to move the trailer.

So, you can see it’s not exactly easy to define the exact stopping power of any cartridge. There are numerous variables involved, but you don’t have to be a rocket scientist to figure out the basics.


This is an important factor, whether you’re on a budget or not. Of course, no single firearm can do everything, but certain guns can do most things sufficiently well. The AR-15 is one of those flexible guns.

It’s easy enough to upgrade your AR by adding new uppers and mags. Rather than wasting time (and money) getting all the possible options, you should research the available cartridges for the AR so you’re not tempted to purchase too much cartridge for the job you intend for it.

Consider that you’re probably upgrading for home defense, hunting, or competition shooting. You’re probably tempted to show off by getting the strongest round you can find. But, you’ll pay for that in extra materials, not to mention the impact of said round to your body from recoil.


It’s not a myth that when you purchase a gun, you have to feed it. This is especially true if you plan to do any target shooting; even if your AR is for home defense, you’ll want to stay sharp with it.

And that means shooting it, regularly.

You won’t want to upgrade your AR to a round that’s difficult to find. And you should take into account the cost of the round you plan to upgrade to. The more rare the cartridge, the higher the cost will be.

Consider the struggle to find ammo during a scare, when ammo is in high demand, or when there’s a low supply. Shipping ammo can be banned by states at any time, and once that happens, it can take a lot of time and effort to overturn. California gun owners are well aware of this fact. Buying ammo online has become the best way for many shooters to get their supplies.

None of the alternate AR cartridges are going to replace the 5.56. Costs of the 5.56 have come down, but they’re still the choice of NATO and police forces, so getting the rounds might always be a problem, either in cost or supply.

5 Most Common Alternate AR-15 Calibers

Let’s take a quick look at the common alternate AR rounds and see what kind of changes you’ll need to make to your AR.

Cartridge Cost of Rounds Changes Needed Uses
.300 Blackout Low Barrel Defense, hunting, target shooting
6.8 SPC Low Barrel, bolt, mags Competition, hunting
6.5 Grendel Medium Barrel, bolt, mags Competition, hunting
.458 SOCOM High Barrel and bolt Hunting
.50 Beowulf High Barrel and bolt Hunting

You should also compare ballistics for each of these AR rounds.

Cartridge Velocity Energy Drop @ 300yds Effective Range
.300 Blackout 125 [email protected] 1300 ft-lbs -25” 350 yards
6.8 SPC 110 [email protected] 1500 ft-lbs -19” 450 yards
6.5 Grendel 120 [email protected] 1600 ft-lbs -18” 450 yards
.458 SOCOM 300 [email protected] 1800 ft-lbs -53” 200 yards
.50 Beowulf 400gr @ 1800fps 2878 ft-lbs -50” 200 yards

So, let’s take a look at these alternative AR round in greater detail and discuss the pros and cons of each.

1.   .300 AAC Blackout (.300 BLK)

image of the .300 AAC BlackoutThis round was designed as a replacement for the sub-machine gun MP5SD, which shot the same 9mm as pistols. Because it was based on the M4 rifle, it needed to match or exceed the subsonic 9 mil and be as quiet as possible.

Advanced Armament Company (AAC) took a .223 casing, blew it out to a .30 caliber, and filled it with pistol powder. And that’s it!

It’s a juiced-up cartridge for the AR-15 and it requires only a barrel change to make it work. You won’t have to mess with magazines, lower receivers, or bolt carriers. It’s ready to go!

This is the only semi-automatic cartridge to reliably feed both super- and subsonic rounds without an issue.

You can check out some AR uppers for the .300 at Hardened Arms.

Pros and Cons of .330 Blackout

The .300 Blackout has extraordinary performance from a short barrel and its ability to shoot subsonic ammo without a problem is another bonus.

This round was designed for a barrel around 9 inches and reaches about 95% of full potential with that barrel, making it the best cartridge for short barrel rifles and guns with suppressors.

Using subsonic ammo, this is the perfect setup for home defense if you use a suppressor; it renders it hearing safe. This overcomes the problems with over penetration when used in a confined space.

With suppressed rounds, your effectiveness narrows to just 75 yards and they won’t have much get up and go past 250 yards. Past 300 yards, you get excessive bullet drop.

2.   6.5 Grendel

image of the 6.5 GrendelThis round debuted in the summer of 2004 at the Blackwater Training Facility in North Carolina.

It’s a necked-down 7.62×39, the original AK-47 round, creating a .264 caliber that takes advantage of the excellent ballistics of a 6.5mm bullet.

You can take a look at some 6.5 Grendel uppers for the AR at Alexander Arms.

Pros and Cons of the 6.5 Grendel

One advantage of a 6.5mm bore is the high ballistic coefficient and sectional density. Yeah, I promised no math, so take our word for it, these two factors make this round outperform the 7.62 NATO in terminal and exterior ballistics.

It also shoots flatter, stays supersonic for a longer period, penetrates deeper, and has less recoil than the 7.62 NATO.

This may sound like an advertisement, but the numbers back this up. The 6.5 performs best for both competitive shooting and hunting.

As far as home defense, this is an expensive round at $0.90 to $1.20 per bullet on average. It offers zero advantage within 300 yards and it’s difficult to find the AR uppers with shorter than 20 inch barrels, which is what you want in a home defense rifle.

The cons of using this round include the high level of barrel erosion, price of ammunition, and difficulty in finding proper magazines. Basic parts like the bolt and barrel are expensive as well; the bolt alone might cost you more than $300.

The Grendel magazines are an odd, banana shape like those for the AK, which isn’t bad in itself, but they’re awkward with the lower receiver of the AR-15. And the 6.5mm bore can burn out quickly, which isn’t usually a problem because the ammo is expensive and rare.

3. 6.8 SPC

image of the 6.8 SPCThe 6.8 round was developed for the Army’s marksmanship unit. It was intended as a long-range option for the M4 and they wanted a round to work well for light field use along with exhibition shooting.

It was considered along with the .300 Blackout and 6.5 Grendel as a replacement for the 5.56. Though it performed well at ranges over 250 yards, there wasn’t much point for military use, since any military engagement generally occurs at less than the 250-yard mark. Bison Arms makes some 6.8 SPC Uppers for the AR.

Pros and Cons to the 6.8

This is an excellent round for short-range hunting because it goes further than a .300 Blackout and hits harder than the 5.56.

The 6.8 round is .270 caliber bullet at 115 grains and it maxes out at about 2600fps. It has around 40% more energy than a 5.56, but offers extra penetration because of the bullet mass.

You’ll need to change the barrel and bolt and you can even find them in a package deal, but one disadvantage to the 6.8 is the lack of availability in magazines.

4.  .458 SOCOM

image of the 458 SOCOMThe .458 SOCOM was developed for special operations forces to have some serious punch in close quarters battle. It saw some action in the Middle East because it’s such a man stopper and could be easily suppressed.

It beats other big bore AR cartridges because it performs admirably in a short barrel and rounds are readily available. You can look over some .458 SOCOM AR-15 uppers at Wilson Combat.

Pros and Cons of .458 SOCOM

This round is a necked down .50AE (think of the Desert Eagle) that uses a rapid burning powder and a heavy bullet, making it ideal for SBRs and suppressors.

The .458 isn’t like the .300, whose subsonic rounds make it impractical for hunting. Its 350gr slugs can be used to hunt thin-skinned game within 75 yards.

With subsonic ammo, you’ll see performance like a souped-up .45 Colt and with supersonic rounds, you’ll think you’re using a .45-70 wrapped in an AR-15 package deal.

5.  .50 Beowulf

image of the .50 BeowulfThis is the round that started the big bore AR-15 concept. It’s said to have been developed by the same people who designed the 6.5 Grendel for military use in stopping vehicles at checkpoints as an aid to car bomb prevention. Alexander Arms produces .50 Beowulf uppers for the AR-15.

This monster round packs a punch at both ends and empties your wallet in the process. But the rounds are only produced by a few manufacturers and don’t have premium options for performance hunting.

To keep yourself in ammo, you’ll probably have to learn how to reload. If you’d like to try your hand at reloading, check out our Complete Beginner’s Guide to Reloading Ammo.

Pros and Cons of the .50 Beowulf

There’s no real advantage to this round for home defense; it’s just as effective as an M855 5.56 round and is a deep penetrating bullet. Likely, it would fully penetrate a bad guy and keep going.

For hunting, it’s powerful enough to take down anything in North America, but the key is to get close to your target and use bullets that open reliably to dump all its energy in your target.

As mentioned above, ammunition is rare and costly. If you really have your heart set on the .50 Beowulf, then you’d be better off learning how to reload if you want to have ammunition at all times.

Some Cartridges to Avoid

Now that we’ve discussed some excellent options for AR cartridge upgrades, let’s talk a bit about cartridges to avoid, because there are some of those, too.


This was Russia’s answer to the 5.56 M16 in battle for the AK-74. It’s been maiming soldiers since the 1970s and has a horrible reputation.

When used by some bad guys in Afghanistan, these rounds blew up or ricocheted when they hit something like a wall. They didn’t penetrate well, nor did they kill efficiently; they were more likely to cause superficial wounds.

Years ago, the market was flooded with this ammunition, but that source has now dried up. Changing your AR to this configuration won’t gain you any benefits, except possibly cheaper ammo. But overall, it gives you a less effective firearm.


This true .30 caliber cartridge fires its 120gr bullets at close to 2200fps from a rifle barrel. While this sounds ideal, it’s really not.

It’s a tapered casing and requires an exaggerated, curved magazine and custom lowers to perform well. It also uses a steel cased ammo with a polymer coating; this doesn’t work well in direct impingement weapons that use the gas from a fired round to cycle the action and reload the next round.

This round isn’t any better than the .330 Blackout and you can’t find it in as many loads. It’s also not easily suppressed, so you’re probably better off going to the .300 Blackout.

But if you’re completely sold on the 7.62, make sure to find a custom lower receiver that moves the pistol grip back to accommodate the magazine required.

Final Thoughts

When you’re looking to upgrade your AR-15, you’ll need to consider a compromise between power, cost, and availability of parts and ammunition.

Some AR upgrades come with a high price tag, so you might need to learn about reloading ammo if your heart is set on these cartridges.

In addition, some of these newer cartridges may fade away in the future, so you may end up doing another upgrade if your rounds disappear.

Decide what’s the most important job you’re upgrading for: is it hunting, competition, or home defense?

The answer to this question will get you closer to choosing the right cartridge upgrade for your AR-15.

Related Reads:

3.3/5 (6 Reviews)
Hey everyone I'm Chris. Founder and editor at Gun News Daily. This site was originally started by my father who passed it on to me. Gun News Daily has been reporting on gun news and conservative politics since 2001. We are the original gun news source. Life-long Second Amendment Supporter.


  1. Has there been significant interest and development in mid-range AR platforms (i.e., between traditional AR-15 and AR-10 sizes) in .277-.284 calibers? I find the AR-15 and AR-10 options to be limiting, especially when considering a piston-operated rifle. Thanks.

  2. The 6.5 Grendel section is full of misinformation!

    “Basic parts like the bolt and barrel are expensive as well; the bolt alone might cost you more than $300.”
    The most well regarded 6.5 Grendel bolt is the JP bolt. These run about $140 at current time. You can get a good quality bolt and bolt carrier for around $150

    “The Grendel magazines are an odd, banana shape like those for the AK, which isn’t bad in itself, but they’re awkward with the lower receiver of the AR-15.”
    Grendel Mags are not banana shaped like AK Mags. The company who created 6.5 Grendel, Alexander Arms, sells GI style steel mags that outwardly look identical to any other 5.56 GI mag. The Grendel was originally based on the 7.62×39, but it does not have the same taper as this round. The magazines are not banana shaped.

    “And the 6.5mm bore can burn out quickly, which isn’t usually a problem because the ammo is expensive and rare.”
    i don’t know where to start with this. The bore of the round has nothing to do with how fast it burns out. This is determined by the amount of powder being burned, in relation to the bore of the cartridge. The Grendel is very easy on barrels, and it pushes a relatively small amount of powder through the 6.5 bore. That is why .223 is easy on barrels, and 22-250 is a barrel burner. Same bore diameter, but more powder being burned.

    Let’s compare a 55 gr .223 to a 120 gr 6.5 Grendel(per nosler load data):
    a 55 gr .223 has a max charge of 26 grains of ramshot TAC.
    a 120 gr 6.5 Grendel has a max charge of 28 Grains of ramshot TAC.

    That is only an extra 2 grains of powder with a jump from .224 to .264 diameter bore.

    Please update the information in this article or take it down.

    • Yea u can get a off the shelf bca or anderson complete upper in 6.5 for under 400$. Faxon and ballistic makes good stuff for under 300$ in 6.5. Also 7.62×39 in a ar15 is reliable if u buy good mags and ammo is readly available. I dont know were he got his info from. I have both 7.62×39 an 6.5grendel platforms. Both cost me under 600$ to build and run flawless

    • Absolutely agree with everything you said Lars Grizzy would too along with Bill Alexander. I’ve posted along the same lines here myself

  3. I have a ar15 in 7.62×39. Very reliable gun. Never had any issues with. U dont need a special lower. A differnt barrel bcg and mag is all u need. Ammo is cheaper than 300blackout and hunting rounds are readly available. Winchester makes good ammo in 7.62×39. The key to a reliable 7.62×39 ar is good mags. Cproduct makes the best mags for it and asc mags are decent too. As far as the 6.5 grendel, they are not expensive to build. Bca and anderson makes complete uppers for under 400$. Faxon and ballistic advantage makes nice barrels for around 250$. Toolcraft makes complete 6.5g bcg for around 100$. Asc and cproducts makes good mags for under 20$ for 6.5g. Only correct statement is ammo is harder to find than other calibers, its almost always sold out at most sporting good places

  4. If you’re going to bring up the .458 Socom, then it’s brother the .375 Socom deserves some attention. I just ordered an 18” upper from Tromix. Apparently the whole setup currently benefits most from handloads from what I understand, but factory loads do exist from SBR Ammunition.

  5. Grendal upper complete w/type 2 bcg from PSA is $319.00.
    Match ammo for 1.20 a round. Plinkers for 60 cents.

    .450 bushy will do what a .458 socom will. Plus deer legal in like 28 states. Ammo readily available and cheap compared to .458.

    Very misinforming article IMHO.

  6. You need to make one edit to the above web site copy on this article. Your heading for the .300 Blackout says “PROS AND CONS OF .330 BLACKOUT” It’s not a .330 Blackout – obviously – so you might want to fix that! :>) Thanks for a good article.

  7. I Agreed with a lot of what you had to say in this article. However as a person who may or may not have participated in a few argument about 6.5 that actually took place in the Late 2004. (Said with a smirk) After Travis Haley made believers out of a lot of individuals in the 6.5 Grendel at The battle of Najaf 04/04/04. He’s a former force reconnaissance marine the same as myself. Not a scout sniper and was engaging targets at 800 to 1000 m plus. My Quam is in the the effective range of the 6.5 and it’s availability. Receivers and whole weapons are available from just about every source imaginable today. This includes the third largest AR manufacture Anderson manufacturing. Ammunition is readily available just about everywhere nowadays and as cheap as 0.25 cents around. The magazine issue you discuss with it and the 7.62 x 39 is a non-issue. It’s absolutely a matter of inserting and extracting a magazine it’s no different than learning how to properly insert the original style magazine then it is to insert this one with no issue with the mag release button and the angle of the magazine it’s just a matter of learning your weapons platform. Reliable high-quality magazines are available from just about every source in today’s market. As far as the 7.62 in the AR platform there are certain environments where 556 ammunition is not readily available but the 7.62 x 39 is and when it comes down to self-defense or other engagements of this type I would much prefer to have the 7.62 x 39 in an AR platform then the 556. I would suggest you re-investigate your first HAND knowledge on both of these platforms have a nice day

  8. Don’t discount the 458 Socom. Nobody begins to look into the round versatility. Taking the parent .458 projectile there are currently 50+ different bullets offered between 185gr to 600gr. Way more versatile than any round available in any caliber.

  9. A lot of the information posted here is wrong it’s clear the author has a limited understanding. The 6.5 is based off of the 220 Russian not the 7.62×39. Yes the 7.62×39 is also based off of the 220 Russian. It’s not more expensive for complete uppers than the others. You missed so many good choices maybe because you wasn’t paid to write about them so sad, I just hope no one used your insights to buy or not buy a weapon.

  10. Without reading the article– or more properly waiting to do so–let me point out an error. An “AR platform” rifle in .300 Blackout is not an AR-15. Neither are the other calibers other than .223/5.56X45. That pickiness is significant in states like MD which define AR-15s as assault rifles illegal for transfer. The platform is not restricted in MD.

  11. Another good point about the .458 SOCOM is that it was specifically designed to work from standard GI mags. Most AR-15 owners have many of these. A 30 round 5.56 mag becomes a 10 round .458 mag; a 20 round mag becomes a 7 round mag. The .458 round is fatter, and therefore loads single stack.

  12. Good information in the article. I’m with much of the group with regards to the 7.62×39 AR chambering i.e. I’ve had great luck with it. I have a shooting partner who built one first, and we were impressed with the reliability and accuracy (C-Products mag, cheap ammo, converted upper).

    I later built a pistol version with PSA’s KS-47 lower which takes AK mags. I’ve got lots of rounds through it with no issues, and it’s sufficiently accurate for a 10″ gun.

    The old Russian round has been tested extensively (google it) in short barrels, and it works quite well, some say surprisingly well. To me it makes a much better, cheaper, and safer alternative to the .300 Blackout. I was actually prepping a .300 Blackout build when I learned that the .300 round feeds just fine in a .223 gun. Of course, it blows the gun up if fired, but it feeds just fine. LOL! So, that being the case, since I have .223 guns, I figured it was safer to do the 7.62×39 build. It’s one less thing I have to worry about.


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