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

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:

• .300 Blackout

• 6.5 Grendel

• 6.8 SPC

• .458 SOCOM

• .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).

POWER

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.

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.

FLEXIBILITY

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.

AVAILABILITY

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.

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

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)

This 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

This 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.