The 3 Best 300 Blackout Uppers You Can Buy

Key Takeaways

  1. When buying a 300 Blackout upper, you want it to include a bolt-carrier group and charging handle, a free-floating handguard, and a barrel that’s between 7 and 12 inches long.
  2. The three best 300 Blackout uppers are the Radian Weapons Model 1, Noveske Gen lll Shorty, and the BCM MCMR-8.
  3. It’s perfectly legal to buy a 300 Blackout upper with a barrel less than 16-inches long without registering it as an NFA firearm (keep reading for details).

The AR-15 is the most popular rifle in America, and for good reason.

It’s reliable, simple, lightweight, and—perhaps most importantly—infinitely customizable.

One of the most unique aspects of the AR-15 is that you can configure it to fire a long list of various cartridges by swapping out part of the rifle—the upper receiver.  

This doesn’t always work as well in practice as it does on paper, though.

Some rounds require special magazines, others jam more often than they should, and others cause excess wear and tear on the gun.

You won’t run into those problems with the 300 Blackout cartridge, though.

The 300 Blackout cartridge was designed from the ground up to be fired through AR-15s, and as a result it doesn’t suffer from any of the reliability problems of other cartridges.

Not only that, but it’s also more powerful than 5.56 when fired through short-barreled rifles or when using subsonic ammo.

So, if you want to turn your AR-15 into a short-barreled rifle or AR-15 pistol, you want to use a 300 Blackout upper.

That just leaves the question of which 300 Blackout upper is best?

Well, that’s what you’re going to learn in this article.

By the end, you’ll know what an AR-15 upper receiver is, which 300 Blackout upper receiver you should buy, and how to install it.

Let’s get started.

What Is an AR-15 Rifle Upper?

If you want to shoot a new kind of cartridge out of most guns, you either have to buy a completely different gun that’s custom designed for that cartridge, or pay a gunsmith to install a new barrel on your existing gun.

That’s not the case with the AR-15, though.

If you want to shoot 300 Blackout ammo (and many other kinds) through your AR-15, you can switch the barrel in less than a minute with no tools, at a typical office desk.

How?

This neat little feature stems from how the AR-15 rifle is constructed.

The AR-15 is composed of two main sections held together with two pins:

  1. The upper receiver group (the “upper”)
  2. The lower receiver group (the “lower”)

You can think of these as two halves of the AR-15.

Here’s what the two sections look like when they’re separated:

300 blackout upper for sale

An AR-15 Upper and Lower

The upper receiver group (upper) consists of the . . .

  • Upper receiver, which is the metal frame that holds the rest of the parts of the upper together.
  • The rail or handguard, which wraps around the barrel and protects it from damage, protects your hand from the hot barrel, and provides space for endless attachments.
  • The barrel, which screws on to the front of the upper receiver.
  • The bolt carrier group, which holds the cartridge in the chamber, extracts the spent case after the cartridge is fired, and holds the firing pin.
  • The charging handle, which you use to retract the bolt-carrier group so that it can transport a cartridge from the magazine to the chamber.

The lower receiver group (lower) consists of the . . .

  • Lower receiver, which is the metal frame that holds the rest of the parts of the lower together.
  • Trigger assembly, which consists of the trigger and several pins and springs.
  • The hammer, which slaps the back of the firing pin and makes the gun go “bang.”
  • The safety switch, which deactivates the trigger and prevents the gun from going “bang.”
  • The pistol grip (if you live in a free state where these aren’t banned), stock, and magazine well (the space where the magazine locks into the gun).

The heart of the upper is the barrel, which is tailor made to work with only one kind of cartridge.

Sometimes you can get away with firing different bullets out of the same barrel, but this can cause excess wear and reduce the accuracy of your shots. For example, you can fire 5.56 bullets out of a barrel designed to fire .223, but it’s not generally recommended.

The lower, though, is more or less cartridge agnostic. As long as the cartridges you want to use will fit in AR-15 magazines, then they will likely work in any AR-15 lower receiver group.

Although this wasn’t the original intention behind this design, this two-piece structure allows you to fire myriad different cartridges through the AR-15 by simply changing the upper.

This is a major advantage, because . . .

  • You only need to buy one AR-15 lower, but you can fire many different cartridges through it if you buy multiple uppers.
  • You can fire all of these cartridges through what looks and feels like more or less the same gun, which means you don’t have to get used to shooting and cleaning a new rifle.
  • You can legally own one gun on paper, but have the ability to fire many different cartridges through it, because the lower is the only part of the gun that’s regulated or tracked by the government. (Not important in my opinion, but worth knowing if you’re concerned about the government keeping tabs on your arsenal).

For example, you can put any of the following uppers on any AR-15 lower . . .

  • 300 Blackout
  • 5.56
  • .223 Remington
  • 5.45×39
  • .224 Valkyrie
  • 6.5 Grendel
  • 6.8 SPC
  • .50 Beowulf
  • .22 Nosler
  • .45 Bushmaster
  • .458 SOCOM

. . . and it’ll shoot without any other modifications.

All AR-15 uppers are standardized to work with AR-15 lowers, so you know that the two parts will always match, too.

Summary: An AR-15 rifle upper is the portion of the gun that contains the barrel, bolt-carrier group, charging handle, forward assist, and handguard. You can fire many different kinds of ammo out of an AR-15 by pulling out two pins, swapping out the upper, and installing a new one chambered for a different cartridge.

What Is the 300 Blackout?

The 300 Blackout, officially known as the 300 AAC Blackout or 300 BLK, is a cartridge designed to be fired through AR-15 rifles with shorter-than-average barrels.

Short-barreled rifles are rifles that have a barrel that’s less than 16 inches long, and they have a number of advantages over rifles with standard-length barrels:

  1. They’re significantly more maneuverable in confined spaces, like inside a building, vehicle, or dense woods.
  2. They’re still relatively compact when you put a suppressor on them, which typically adds about 6 to 12 inches to the length of the gun.
  3. They allow you to aim at and transition between targets faster than rifles with longer barrels.

Here’s what a short-barreled rifle looks like compared to a normal rifle:

300 blackout upper rifle pistol

A standard rifle vs. a short-barreled rifle.

The problem with short-barreled rifles, though, is they also significantly reduce the power of the cartridges you’re shooting through them.

For example, reducing the barrel length of an AR-15 from 20 inches to 10.5 inches also reduces the bullet energy by around 35%. This makes the cartridge far less lethal, and also reduces its effective range.

The 300 Blackout changes that.

Despite being about the same size as 5.56 ammo, the 300 Blackout is significantly more powerful when fired through short-barreled rifles.

For example, when using supersonic ammo, a 300 Blackout bullet fired through a 10.5-inch barrel has more muzzle energy than a 5.56 fired through a 16-inch barrel.

The end result is that you can fire much more powerful bullets than 5.56 through a smaller, more compact rifle.

The 300 Blackout was also designed to be more lethal than 5.56 ammo when using subsonic bullets, which are easier to suppress than normal ammunition. Subsonic bullets move below the speed of sound, which allows you to make a gun nearly “Hollywood” quiet when paired with a suppressor.

Subsonic 300 Blackout bullets have anywhere from two to four times more energy than subsonic 5.56 bullets. What’s more, subsonic 300 Blackout ammo is also more reliable when used in an AR-15.

Finally, you can also load 300 Blackout ammo into 5.56 magazines.

Advanced Armament Corporation—the company that created 300 Blackout—rigorously tested a variety of designs to make sure 300 Blackout fit flawless into AR-15 magazines, fed into the gun, and fired without a hitch.

If you want to fire 300 Blackout through your AR-15, all you have to do is buy a 300 Blackout upper, slap it on your AR-15 lower, load up your AR-15 mags with 300 Blackout ammo, and start shooting.

This makes the 300 Blackout one of the most versatile and convenient cartridges you can shoot in an AR-15.

Summary: The 300 Blackout is a rifle cartridge designed for AR-15s that’s significantly more powerful than 5.56 when fired through a short barrel or when using subsonic ammo. It’s also designed to work seamlessly with the AR-15 when used with a 300 Blackout upper.

How to Choose the Best 300 Blackout Upper

Now that you know what an upper is, and which cartridge you want to shoot (300 Blackout), it’s time to pick an upper.

Luckily, choosing a good upper is a simple process.

There are just three questions you need to ask yourself:

  1. Does it require any extra parts to work?
  2. What’s the best 300 Blackout barrel length?
  3. What kind of handguard do you want?

Of course, you can always dive even deeper than these questions, and look at things like the machining techniques used to make the upper, but that’s typically unnecessary.

So long as you purchase a 300 Blackout upper from a reputable manufacturer, like the ones I recommend below, you can trust it’s going to hold up, perform well, and retain its value.

Does It Require Any Extra Parts to Work?

Most AR-15 uppers come with all of the parts you need, so you can slap them on a lower, load in a mag, and start shooting.

That’s not always the case, though.

Often, AR-15 lowers are sold without the bolt-carrier group or charging handle, which you have to purchase separately.

This is worth remembering, as you’ll often find low-priced 300 Blackout uppers that seem like a great deal, when in fact the reason they’re so cheap is they don’t include all of the parts you need.

Manufacturers don’t do this to be malicious, though. They do it so you can mix and match which parts you want.

The two main parts that people will swap out on an upper receiver are the charging handle and the bolt-carrier group, so many manufacturers don’t include the components.

Here’s what the charging handle looks like:

radian weapons charging handle

A Radian Weapons Charging Handle

And here’s what the bolt-carrier group looks like:

radian weapons bolt-carrier group

A Radian Weapons Bolt-Carrier Group

For example, I’m a huge fan of Radian Weapons’ Raptor charging handles (shown above), and I like to install them on my AR-15s whenever I can. Therefore, I prefer to buy upper receivers without charging handles, so I don’t end up with an extra that I don’t use.

Likewise, many people like to buy aftermarket bolt-carrier groups from companies like Bravo Company, Radian Weapons, or Brownell’s.

The bottom line is that if you have a particular charging handle or bolt-carrier group you’d like to use with your new 300 Blackout upper, try to find an upper that doesn’t come with these parts.

If you just want something that works right out of the box, buy a complete upper receiver that includes a bolt-carrier group and charging handle (like one of the ones you’ll see in a moment).

Summary: If you want an upper receiver group that works right out of the box, buy a complete upper receiver with bolt-carrier group and charging handle.

What’s the Best 300 Blackout Barrel Length?

The barrel is the most important and variable part of most AR-15 uppers.

You can find 300 Blackout uppers with barrels ranging from 5 inches all the way up to 16 inches, and different length barrels can have a massive impact on the performance of the rifle.

On the one hand, longer barrels will give your bullets more energy, which equals better killing power and longer range.

On the other hand, longer barrels also add a significant amount of weight to your gun and make it more awkward to hold, aim, and shoot with than short barrels. Plus they don’t look cool.

Since you’re looking for a 300 Blackout upper, I recommend you go with a barrel that’s 7 to 12 inches long.

A barrel less than 7 inches long will significantly reduce the energy of a 300 Blackout bullet, whereas a barrel more than 12 inches long will only give you marginal improvements in energy and velocity for every additional inch of barrel.

Within this range, though, what barrel length you get mostly depends on personal preferences.

I like a 7 or 8-inch barrel on 300 Blackout rifles, since that offers the most compact, ergonomic package. I also like to attach a suppressor to most of my 300 Blackout rifles, so I want the barrel to be as short as possible to minimize the overall length of the gun.

For example, here’s what a 16-inch barrel upper looks like next to an 11.5-inch upper with a suppressor:

sbr with suppressor

Very nice, indeed.

Now, one downside to using a short barrel on most AR-15s is that your face is going to be closer to the muzzle. If you’re shooting a lot, this means more pressure, gas, and powder flying back into your face.

The good news is that this is mostly an issue with 5.56/.223 AR-15 uppers, not with 300 Blackout uppers.

300 Blackout was designed to efficiently burn up its propellant and release its pressure from short barrels, which equals a smaller fireball, less muzzle blast, and less unburnt powder hitting you in the face.

If you plan on using a suppressor, though, this isn’t an issue for either 5.56 or 300 Blackout. The suppressor will push the gas farther in front of your face where it won’t be as annoying.

Assuming you get a barrel that’s between 7 and 12 inches long, you also want to make sure the twist rate is 1:5 or 1:7. This means the bullet rotates once per 5 or 7 inches of barrel, which improves the accuracy of heavy subsonic 300 Blackout bullets.

Summary: Get a 300 Blackout upper with a barrel that’s 7 to 12-inches long, and make sure it has a twist rate of 1:5 or 1:7.

What Kind of Handguard Do You Want?

The handguard of an AR-15 is the tube of metal or plastic that surrounds the portion of the barrel closest to the shooter.

Here’s what it looks like:

geissele AR-15 handguard

An AR-15 handguard.

And here’s what it looks like on an AR-15:

geissele AR handguard

An AR-15 handguard attached to a rifle.

If the handguard is made of metal you’ll also hear it referred to as the “rail.”

You can loosely divide handguards into two categories:

  • Non-free floating (or “drop in”) handguards.
  • Free-floating handguards.

A non-free floating handguard is one that directly touches the barrel. These tend to be cheaper and are what you’ll find on most budget AR-15s, but they also tend to overheat faster, break more easily, and compromise accuracy more than free-floating handguards.

On the other hand, free-floating handguards don’t touch the barrel (hence the barrel remains “free floating” inside the handguard).

You want to go with a free-floating handguard if your budget allows.

Next, you need to choose what kind of attachment system you want on your handguard.

You see, most handguards have holes cut in them that allow you to attach various accessories like lights, lasers, sights, scopes, and so forth.

You have five options here:

  1. M-Lok
  2. Keymod
  3. Picatinny
  4. Proprietary
  5. No attachment system

M-Lok and Keymod are the most common systems because they’re lightweight, durable, and don’t add much bulk to the rifle.

M-Lok features a series of rectangular holes cut into the handguard, like this:

BCM M-Lok Handguard

An M-Lok handguard.

Keymod featured a series of keyhole-shaped holes cut into the handguard, like this:

bcm keymod handguard

A keymod handguard.

Both M-Lok and Keymod work just fine, although a test conducted by the Naval Surface Warfare Center found that M-Lok was more durable and did a better job of securing accessories when subjected to repeated drops and other abuse.

Picatinny is an older system that features a series of raised grooves, like this:

picatinny handguard

A picatinny handguard.

The advantage of this system is that it’s very easy to use, it’s remarkably durable, and it maintains the accuracy of optics better than most other systems. The downside is that it’s heavy—really heavy.

Most AR-15 uppers have a picatinny rail on the top, where optics are generally mounted, and then have M-Lok or Keymod holes on the sides and bottom of the handguard.

Some companies have proprietary attachment systems, like this one from LWRC:

lwrci handguard

An LWRCI proprietary handguard.

Most of these systems are just holes that allow you to attach small sections of picatinny rail, which you can then mount accessories to. Unless you have a specific reason to go with a proprietary system, I suggest you stick with the tried and true options of M-Lok, Keymod, and Picatinny.

Finally, some handguards don’t have any attachment system. This is fine if you don’t plan on putting any flashlights, lasers, and so forth on your gun, but a non-starter if you do.

In most cases, I recommend you go with M-Lok.

Although it’s not drastically different from Keymod, it’s probably a little more durable, accurate, and secure, and costs the same.

If you already have a bunch of Keymod-compatible accessories, though, then get a Keymod handguard. The differences aren’t big enough to justify doing a makeover of your accessories.

Summary: Get a free-floating handguard with either M-Lok or Keymod attachment systems. M-Lok is generally the best option for most people.

What’s the Best 300 Blackout Upper?

At this point, it’s hard to find a company that doesn’t produce a 300 Blackout upper for AR-15s.

Many of these companies appear to offer almost identical products at wildly different price points, making it tough to decide whether you’re paying for marketing hype or quality.

It’s also hard to say what the “best” 300 Blackout upper is, as this definition will vary depending on what you’re doing. The best upper for target shooting will be different from the best upper for hog hunting.

That said, I’ve included what I believe to be the best all-around 300 Blackout uppers for most purposes.

I haven’t tested every 300 Blackout upper out there and I’m sure some worthy contenders have fallen through the cracks, but I’ve tested enough and talked with enough shooters to point you in the right direction. (As always, let me know in the comments if you have any suggestions!).

The Best 300 Blackout Upper Overall

The Radian Weapons Model 1 9-inch 300 Blackout Upper

300 blackout upper

The Radian Weapons Model 1 9-inch 300 Blackout Upper

This is a 300 Blackout upper with a 9-inch barrel and a 9-inch rail.

It’s also the best fully assembled 300 Blackout upper you can buy.

The barrel is made of polished 416R stainless steel, a metal that is significantly tougher, more corrosion resistant, and better at maintaining accuracy after thousands of rounds than typical carbon steel.

(There are anecdotes of people shooting over 12,000 rounds through 416R stainless steel barrels using much more powerful rounds than 300 Blackout).

The upper and the handguard are machined from 7075-T6 aluminum, which is a particular aluminum alloy with a much higher strength to weight ratio than other forms of aluminum. It’s typically used in products like airplane frames, bicycle components, and lacrosse sticks, where you need maximum strength and minimal weight.

The bolt carrier group is a custom design from Radian Weapons that reduces friction when firing, and it’s nitride coated for a smooth, low-friction, extremely durable finish.

It comes with a Radian Raptor-SD™ Suppressor-Optimized Ambidextrous Charging Handle, which reduces the amount of gas, oil, and unburnt powder that blasts into your face when using a suppressor.

It also comes with a SilencerCo ASR flash hider or a Dead Air flash hider/muzzle brake, depending on what kind of suppressor you may want to use.

Whether you plan on using a suppressor or not, I recommend the Dead Air flash hider/muzzle brake. Muzzle brakes are generally more helpful than flash hiders, and Dead Air makes better silencers than SilencerCo. Only get the SilencerCo ASR flash hider if you already own a SilencerCo silencer.

Finally, every part of this upper has been designed to minimize sharp corners and unnecessary protrusions and channels to make it sleek, light, and attractive.

The bottom line is that if you want the best 300 Blackout upper money can buy, you want the Radian Weapons Model 1 9″ 300 Blackout upper.

Check it out on Radian Weapons’ website:

Radian Weapons Model 1 9-inch 300 Blackout Upper ($1,435)

The Best 300 Blackout Upper Runner Up

Noveske Gen III Shorty 10.5-inch 300 Blackout Upper

noveske 300 blackout upper

The Noveske Gen lll Shorty 10.5-inch 300 Blackout Upper

This is a 300 Blackout upper with a 10.5-inch barrel and a 9-inch rail.

You could look at this like the Mercedes of 300 Blackout uppers. It’s not overly flashy or filled with fancy features, but it elegantly executes all of the basics and just works.

All of the parts are precision machined to match perfectly, it’s coated in black Cerakote for corrosion, heat, and scratch-resistance, and the 300 Blackout version comes with a Cherry Bomb muzzle brake from Q, so it’s compatible with their suppressors.

The barrel features a 1:7 twist and is made of stainless steel for durability and corrosion resistance.

In many ways, this upper is on par with the Radian Weapons Model 1. The main reason I’ve chosen to put it in second place is because it doesn’t look as nice and uses a 10.5-inch barrel instead of a 9-inch barrel on the Model 1, which adds weight for little added muzzle energy.

One advantage it has over the Model 1, though, is that it also comes in a Keymod version, if that’s important to you.

The bottom line is if you want one of the best 300 Blackout uppers on the market, you want the Noveske 10.5-inch Gen III Shorty 300 Blackout Upper.

Check it out on Noveske’s site (make sure you select the 300 Blackout version with the M-Lok handguard):

Noveske 10.5-inch Gen III 300 Blackout Upper ($1,335)

The Best 300 Blackout Upper for the Money

Bravo Company Manufacturing (BCM)  MCMR-8 9-inch 300 Blackout Upper

bcm mcmr 300 blackout upper

The BCM MCMR-8 9-inch 300 Blackout Upper

This is a 300 Blackout upper with a 9-inch barrel and an 8-inch rail.

BCM has a reputation for providing products that are on par with much more expensive companies for a more reasonable price, and this upper is a good example.

Like almost all of BCM’s barrels, the barrel is chrome-lined for durability, corrosion resistance, and heat tolerance.

The outside of the barrel is coated in a manganese-phosphate finish, which is similar to nitriding and wards off pitting, rust, and scratching.

The inside of the barrel features a 1:7 twist, which as you learned earlier is a good middle-ground for shooting super- and subsonic 300 Blackout bullets.

The whole package also weighs in at only 2.2 pounds without the bolt carrier group and the charging handle. In fact, that’s just about the only downside about this upper receiver group is that you have to pay extra for the bolt carrier group and the charging handle, which bumps up the price by about $220.

To be fair, BCM does this because many people like to buy their own bolt carrier group and charging handle, not because they’re trying to short-change you.

If you want one of the best 300 Blackout uppers around without paying an arm and a leg, you want the BCM 300 Blackout 9-inch MCMR-8.

Check out out on BCM’s website:

BCM 300 Blackout 9-inch MCMR-8 Upper ($640 to $889)

Wait, Aren’t Short-Barreled Rifles NFA Firearms?

Indeed, but short-barreled uppers are not.

In case you aren’t familiar with the term, NFA stands for National Firearms Act, a piece of legislation that puts additional restrictions on particular guns that the Ministry of Truth federal government signed into law in 1934.

Any firearms listed in the NFA are considered “NFA Firearms,” and are regulated under the laws of the NFA.

The main categories of NFA firearm are:

  • Short-barreled rifles
  • Machine guns
  • Silencers (obviously not a gun, but the federal government legally considers them guns, hurr durr)

A short-barreled rifle is legally defined as a rifle with a barrel less than 16-inches long or or an overall length of less than 26 inches.

Now, an upper receiver—like the ones you just learned about—is not considered a short-barreled rifle until you attach it to an AR-15 lower receiver. Then all NFA rules apply.

This process would be legally considered building a short-barreled rifle, and if you want to do this, you need to go through the process of applying for an NFA firearm before you build it.

To jump through the NFA hoops, you need to fill out and submit ATF Form 5320.4 (aka “Form 4”) to both the ATF and your chief law enforcement officer, submit two passport photos, submit two fingerprint cards, and pay the ATF $200 for every NFA item you buy.

Oh, and the approval process generally takes 6 to 12 months.

In other words, it’s a pain in the ass.

The good news is that if you want to have a short-barreled rifle, there’s a comically simple workaround:

Buy or build an AR “pistol” instead.

You see, the laws regarding short-barreled rifles only apply to rifles which have a traditional stock, which looks like this . . .

radian weapons model 1 sbr

A short-barreled rifle with a traditional stock.

The NFA rules don’t apply to rifles that have a pistol stabilizing brace (usually just called a brace) which looks like this . . .

radian weapons model 1 pistol

A “pistol” with a pistol-stabilizing brace.

Or this . . .

ar-15 pistol

Another “pistol” with a different kind of brace.

Or this . . .

honey badger pistol

Another “pistol” with an even cooler brace.

Here’s another comparison of a rifle versus a “pistol,” just to hammer the point home:

honey badger pistol vs sbr

A rifle on the left, a pistol on the right.

So, if you want to avoid the tangle of buying an NFA firearm, buy a short-barreled 300 Blackout upper and put it on a lower that has a brace instead of a standard stock. Then you own a “pistol,” not a rifle, and you don’t need to worry about NFA laws.

What’s more, you don’t need to ask the government permission to travel across state lines with a pistol, but you do need to ask permission before travelling with an NFA firearm.

If you’re worried a brace won’t feel as secure as a regular stock, don’t. Braces don’t feel quite the same, but the differences are small enough that most people would rather just buy or build a “pistol” AR. Of course, there’s no reason you can’t have both a pistol and a short-barreled rifle. 🙂

So, if you want to stay within the law while enjoying a great 300 Blackout upper, you have three options:

  1. Buy a 300 Blackout upper with a barrel less than 16-inches long and put it on a lower that has a brace instead of a standard stock, and be on your merry way.
  2. Buy a 300 Blackout upper with a barrel less than 16-inches long and put it on a lower that has a standard stock, and go through the process of buying an NFA firearm.
  3. Buy a 300 Blackout upper with a 16-inch barrel (booo) so you don’t need to worry about the NFA laws.

If you’re just getting started with 300 Blackout, I recommend you go with option one.

Finally, it’s also legal to buy a short-barreled 300 Blackout upper and store it while deciding whether you want to buy a lower with a normal stock or one with a brace. In other words, you won’t get in trouble for simply owning a short-barreled upper, as the upper isn’t legally a firearm.

I know this can be confusing, so if you have any questions about this process, leave a comment below and I’ll help you get it sorted out!

Summary: It’s perfectly legal to buy a 300 Blackout upper with a barrel less than 16-inches long without going through the process of buying an NFA firearm. If you attach the upper to a lower with a standard stock, you need to register it as an NFA firearm. If you attach the upper to a lower with a pistol stabilizing brace, you don’t need to register it as an NFA item.

A Word of Warning . . .

Never fire a 300 Blackout round through a 5.56 barrel, or this happens:

300 blackout upper break

What happens when you shoot a 300 Blackout bullet through a 5.56 barrel.

 

300 blackout bullet

What happens to a 300 Blackout bullet when it’s fired through a 5.56 barrel.

That’s what happens when you fire a .30-caliber bullet through a .22-caliber hole—the gun breaks.

Luckily, this problem is easily avoided by clearly marking your magazines, double-checking what upper you have attached to your gun, and keeping your 300 Blackout and 5.56 ammo separate.

The Bottom Line on the Best 300 Blackout Uppers

An AR-15 rifle upper is the portion of the gun that contains the barrel, bolt-carrier group, charging handle, forward assist, and handguard.

You can fire many different kinds of ammo out of an AR-15 by pulling out two pins, swapping out the upper, and installing a new one chambered for a different cartridge.

The 300 Blackout is a rifle cartridge designed for AR-15s that’s significantly more powerful than 5.56 when fired through a short barrel or when using subsonic ammo.

The 300 Blackout was also designed from the ground up to work seamlessly with the AR-15.

If you want to shoot it through your AR-15, all you have to do is buy and install a 300 Blackout upper, load up your regular AR magazines with 300 Blackout ammo, and start shooting.

When choosing a 300 Blackout upper, you need to ask yourself three questions:

  • Does it require any extra parts to work?
  • What’s the best 300 Blackout barrel length?
  • What kind of handguard do you want?

If you want an upper receiver group that works right out of the box, buy a complete upper with bolt-carrier group and charging handle.

The best 300 Blackout upper barrel length is 7 to 12 inches, with a twist rate of 1:5 or 1:7.

Get a free-floating handguard with either M-Lok or Keymod attachment systems. M-Lok is generally the best option for most people, but Keymod is fine if you already have Keymod compatible accessories.

The best 300 Blackout upper overall is the Radian Weapons Model 1 with a 9-inch barrel.

The second best 300 Blackout upper is the Noveske 10.5-inch Gen lll.

And the best 300 Blackout upper for the money is the BCM 9-inch MCMR-8.

It’s perfectly legal to buy all of these uppers. Just remember that if you attach the upper to a lower with a standard stock, you need to register it as an NFA firearm. If you attach the upper to a lower with a pistol stabilizing brace, you don’t need to register it as an NFA item.

Finally, don’t be a goofball and accidentally shoot a 300 Blackout bullet through a 5.56 upper. It’ll ruin your day (and your gun).

What are your thoughts on these 300 Blackout uppers? Have any input on these or recommendations for other uppers? Let me know in the comments below!

Oh, and if you enjoyed this article and want to learn more about how the 300 Blackout cartridge compares to other cartridges, you want to check out the American Arms Guide to Cartridge Ballistics. 

This is guide shows you the muzzle velocity and energy, bullet weight, and bullet drop for over 50 different cartridges, including various kinds of 300 Blackout. Using this guide, you can choose exactly the right kind of ammunition for your shooting goals, whether they be hunting whitetails, defending your family from a home invader, stopping a criminal while on duty, or winning your next shooting competition.

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