The Best .300 Blackout Uppers

Michael Crites

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This article is part of our Guide to Everything AR

Despite all of the lasers, tech accessories, and modern features, the AR platform is more than half a century old.

Originally chambered in .308 as the AR10, Eugene Stoner made a rifle that was chambered for a round that was full of compromises, the 5.56 NATO.

To be fair, we certainly like the 5.56mm: it’s a capable round that’s lightweight, shoots reasonably straight out to about 500 yards, and has been getting the job done since Vietnam.

With that said, we’ve had 50 years or so to optimize the system, and that is exactly what has happened with the .300 BLK round. The .300 Blackout was engineered from the ground up for the AR platform – and it does not disappoint.

If you have ever fired an AR in 5.56mm indoors, whether a range or in some other circumstance, you know that it is, in fact, a seriously bad time for you and anyone north of the barrel in terms of sound, flash, and concussion.

So, in trying to develop a round that hits harder at short ranges, as well as suppresses supremely well, you’ll want to take a look at the .300 BLK. 

In This Article:

.300 Blackout Upper Comparison

Below is my list of the .300 Blackout upper receiver recommendations. I list the best choices in terms of value, performance, design, and cost.

Click on the name to head to the product page, read reviews and check prices or skip ahead to the list of uppers.

NameSelectionLengthPrice
PSA 10.5” Pistol Length UpperBest Value10.5-inch$639
Daniel Defense DDM4 300sPremium Option10.5-Inch$1,237
M&P15 Whisper Upper Receiver Rifle-Length Pick16-Inch$869
Aero Precision M4E1 Assembled Upper Receiver Shortest8-Inch$445
Pro2A Tactical 10.5-inch .300 BLK UpperBudget Option10.5-Inch$319

.300 Blackout Upper Recommendations

1. Palmetto State

For pistol uppers, Palmetto State Armory has put together a sweet offering here. This one has a short barrel that leaves plenty of room beyond the handguard for your desired can, making it perfect for home defense or close quarters.

The PSA PA-15 300 BLK upper, carrier, and charging handle. Simple but effective.
The PSA PA-15 300 BLK upper, carrier, and charging handle. Simple but effective.

We also love the lightweight handguard, which helps prevent it from getting overly front-heavy when mounted with a suppressor. 

PSA .300 BLK Barrel Stamp
PSA .300 BLK Barrel Stamp

That open handguard design, as much as it keeps weight down and helps with thermal performance, may come at the cost of heat transfer to your hands, so think about some gloves when shooting this one.

Running windowed PMAGs in my .300BLK PSA PA-15
Running windowed PMAGs in my .300BLK PSA PA-15

What we liked:

What we didn't:

2. Daniel Defense

Daniel Defense produces some of the best high-speed platforms to more than capable operators – like the U.S. Navy SEALs.

This upper from the folks at Daniel Defense is certainly no exception to their quality. The fit and finish are excellent, and the 10.5-inch barrel is about the perfect length for a .300 BLK pistol. Plus you get all the bells and whistles of a DD upper, including their world-class quad rail handguard.

While not pistol-length, my DDM4A1 uses the same quad-rail, and it's worth every penny.
While not pistol-length, my DDM4A1 uses the same quad-rail, and it's worth every penny.

With the already short length here, the best application for this upper would be to add a short suppressor and use subsonic ammunition. Doing that will let you shoot .300 Blackout indoors without totally ruining your eyes and ears: this makes the DDM4 300s a great entry into this new caliber.

What we liked:

What we didn't:

3. Smith & Wesson

Smith and Wesson have been getting into the AR game really seriously in the past ten years, so it’s great to see them selling an upper in .300 Blackout as well. This one is meant for mainly rifle configurations, and we think it would be especially useful as a hunting rifle when paired with a quality suppressor. 

One thing we might change out were it our gun is the handguard: it has a ton of room to mount anything up to and including the kitchen sink, but the square profile is kind of thick in the hand.

What we liked:

What we didn't:

4. Aero Precision

To round out our picks, we wanted something that would be especially suitable for a pistol built, and the Aero Precision M4E1 is awesome for that in the 8” barrel format. 

It comes with a flash hider, but I recommend fitting a suppressor on it as the length just screams for a can and hand stop. At barrels this short there is no room for error, so a suppressor paired with a hand stop gives you more stability to work with.

You’ll need to bring your own BCG and charging handle but for those who know and rely on the Aero brand and want to keep it short, this is a quality upper. 

What we liked:

What we didn't:

5. Pro2A Tactical

When the folks at Pro2A Tactical reached out about reviewing their products, I was intrigued. I had never heard of the company, but am always up for trying something new, especially when it comes from a smaller manufacturer.

They shipped me a 10.5-inch .300 BLK upper, which arrived quickly, and I found the folks at Pro2A Tactical very easy to work with. 

I was surprized how tight the Pro2A upper fit with my various pistol lowers. It had virtually no slop, and in some cases had a tighter fit than factory uppers.
I was surprized how tight the Pro2A upper fit with my various pistol lowers. It had virtually no slop, and in some cases had a tighter fit than factory uppers.

The upper pairs a Tactical Kinetics 10-inch 4150 Chrome Moly Vanadium Steel, 1:8 barrel with a 9-inch M-LOK Free Floated handguard from Axis MFG built around a 7075-T6 upper receiver, all of which gives the Pro2A Tactical upper a very spartan look. There are virtually no markings on the upper other than the barrel and Cerro Forge keyhole marking.

That straightforward build does, however, help in the weight department — with the Pro2A coming in 3 ounces lighter than my other 10.5-inch pistol uppers. 

The handguard is simple, spartan, and helps keep the build light.
The handguard is simple, spartan, and helps keep the build light.

I swapped a few uppers out with the Pro2A and was surprised by how well it locked up with my various lowers. The fit on a variety of lowers was tighter and had less play than pistol uppers that had been paired with their lowers from the factory — impressive!

But how’s it shoot?

After I was done fiddling with lower pairing and my scale (and waiting far too long for some .300 BLK ammo to arrive), I took it out to the range along with a few hundred rounds of Armscor 147 GR FMJ. It ate everything I put through it and shot as well as any other 10.5-inch upper in my collection. Groupings were tight at 50 and 100 yards (or as tight as I can muster), and I experienced no issues with feeding or reliability.

Another cool trick the Pro2A upper pulls off? It costs less than equivalent uppers from some major brands. 

Taking care of business.
Taking care of business.

If you’re in the market for a quality upper and are bored with shopping big-boy retailers, check out Pro2A Tactical. Working with them is more like shopping at your LGS than Cabelas, and I think supporting small business is something we can all get behind. 

What we liked:

What we didn't:

Why the .300 BLK?

Two AR-15 magazines with the black mag showing off a .300 AAC Blackout and the yellow mag housing a .223 Remington.
While the .223/5.56 NATO (yellow mag) generally runs 55 to 77-grain bullets, the chunky .300 BLK (black mag) starts at about 100 and goes all the way up to around 220-grains. This makes for a slower, more suppressor-friendly round.

The short, stubby round, the .300 BLK, gives you improved performance over the 7.62x39mm at 300 yards. And at close range, the 5.56mm, frankly, is an awful round.

There’s a good reason that Colt made ARs in 9mm going back into the Vietnam era. Indoors and out of short barrels, the 5.56mm makes a ton of noise and even more flash, so it’s really not engineered for CQB or urban combat at all.

Of course, the 9mm approach is only a stopgap measure that lacks stopping power at range. It also requires 9mm-specific components – and you still end up with a sub-par AR full of compromise (or more of a PCC). For military and law-enforcement applications, a .300 Blackout-chambered M4 is a marvelous sub-gun replacement, with a cartridge considerably more effective than a 9mm pistol-caliber MP5.

The same thing can be said for home defense in a .300-chambered AR replacing pistol caliber carbines – lots more stopping power with little fuss.

Best 300 Blackout Rifles - Cover
Taking my BLK to the range

In standard 5.56mm, ARs will hit peak burn out of about a 16” barrel, with 14.5” as short as you can go with a 5.56 barrel and still get performant terminal ballistics, complete powder burn, and a lack of a fireball.

Those longer barrels make them more cumbersome when it comes to close-range applications like home defense.

Instead, we want a short-barreled rifle or pistol that, especially when paired with a suppressor or muzzle brake, can lead to a handy and quiet rifle that still makes more impact than a 9mm, and in most cases, more than 5.56mm.

Tests by AAC way back in 2012 (and of course, ballistics have improved since then) demonstrated that the .300 BLK could still be effective out to 440 yards– when fired from a barrel as short as 9-inches, making it ideal for use in AR pistols.

The circa 2011 Advanced Armament Company's .300 Blackout AR-15 platform
The circa 2011 Advanced Armament Company's .300 Blackout AR-15 platform, achieving impressive performance from just a 9-inch barreled SBR. (AAC Photo via Department of Defense)

When it comes to a bad-breath-distance engagement, we want a .300 blackout.

In addition to its performance characteristics, one of the major contributors to the .300 Blackouts popularity is its compatibility with existing 5.56/223 AR-15 rifle components.

Your bolt carrier groups, upper and lower receivers, magazines, rails, and the like work just as well with the .300 BLK as your 5.56 NATO rounds. Plus, .300 Blackout-chambered AR-15 still uses the same magazines without a loss of capacity, i.e., a 30-round 5.56 NATO AR mag will still hold 30 rounds of Blackout.

Just swap the barrel and gas system and commence pow-pow. Check out our gas system guide for more on that front.

What to look for in a Quality .300 Blackout Upper

AR uppers ready for testing
AR uppers ready for testing

1. The shorter the better

For the .300 Blackout, shorter is better. The round simply doesn’t perform at range they way a 5.56/223 round. It’s a heavier, slower-moving round, but thanks to the .30 caliber bore, will burn its full potential in a 9-inch barrel.

Diamondback DB15 pistol - Handguard
The .300 Blackout gives you better short-barrel performance than a traditional 5.56 NATO

That means that, no, you won’t be punching out targets at a mile. But, inside of 200 yards, you’ll be hitting well above the weight of a 5.56mm. Want more? Take deep dive into AR barrels with our barrel guide.

2. Threaded barrels

Because it moves slower, it’s also a lot quieter: this makes .300 blackout a great choice for a good flash suppressor, a silencer, or a muzzle brake, which requires a threaded barrel.

Shorter barrel lengths are excellent for close-quarters engagements making a .300 blackout rifle or pistol a great option for home defense, but you’ll want to protect your hearing with a suppressor or some other muzzle device. 

First of all, a little legalese will be necessary here. Since .300 Blackout does best out of shorter barrels, we’ll be recommending AR pistols as final builds.

That means that the lower you put it on has to have been registered as a pistol when it was made and that you cannot put a stock or a forward pistol grip on it. But we all love a good brace!

3. Muzzle devices

Muzzle devices ahoy
Flash hider, compensator, or suppressor, a shorter-barreled .300 Blackout rifle or pistol will benefit from some additional muzzle control.

Also, you’ll want to consider what muzzle devices you want to try out. Since we think a high-quality .300 Blackout does so well suppressed, we think a pistol upper with a threaded barrel is the perfect way to get the best out of the round.

A .300 Blackout pistol, with a suppressor, is still only about as long as an average AR15 without a suppressor, so it ends up a really handy package overall, which is one of the things that we like about the round.

Conclusion

With that said, all of the options on this list are good, and we think you could make a great pistol or rifle out of any of them: we recommend thinking about the parts you already have and what you want to do with them before making a purchase. With this guide in hand and a little bit of thinking, you’ll be well on your way to an excellent .300 Blackout pistol or rifle.

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