5 Best .300 Blackout AR-15 Uppers

The AR world is absolutely massive, and you can chamber an AR in everything from .22 LR to .45-70 Government. The AR is often adapted to function in calibers it was never designed for shooting.

While that’s cool when it happens, what's even cooler is when rounds are designed specifically for the AR platform.

One such round is the .300 Blackout. The .300 BLK has easily been the most successful new caliber in the last 20 years.

Read on to see how to get your standard 5.56 AR-15 ready to use .300 BLK.

How We Chose the Best .300 BLK Uppers

The entire team at Pew Pew Tactical had a hand in contributing to this post. Our team comprises prior law enforcement, competition shooters, hunters, instructors, and hobbyists who've spent extensive hours at the range testing and shooting what we recommend.

Our picks were based on the following criteria: Overall build quality, features, accuracy, operating system, availability, and price.

We constantly test gear and regularly update articles as new models become available, so if you’re favorite isn’t here, check back soon!

Best .300 Blackout Uppers

1. PWS MK109 MOD 1-M - Editor's Pick

Editor's Pick

PWS MK109 MOD 1-M .300 BLK Upper

$1049

at OpticsPlanet

Prices accurate at time of writing

$1049 at OpticsPlanet

Midway USA (see price)

Brownells (see price)

Primary Weapons System (PWS) is known for their innovative use of the long-stroke piston system (think AK-47 or M1 Garand) in the AR-15 platform.

Their piston guns are renowned for their accuracy and how well they run suppressed. The long-stroke piston system helps manage backpressure when using a suppressor, while also providing a very pleasant at-ear sound, especially when using subsonic .300 Blackout ammunition.

PWS also guarantees sub-MOA accuracy with match ammunition - something that very few AR companies dare to do.

On top of the accuracy, cleanliness of the piston system, and excellent suppression qualities, these uppers have an extremely nice build quality.

PWS adds some small touches like the Radian Raptor extended charging handle, a Rearden-style suppressor capable 2-port compensator, and a top cutout in the rail to easily access the gas block for adjustment.

They aren't the cheapest uppers, but you are getting some awesome features with an accuracy guarantee to boot. If you are wanting a suppressed .300 BLK build, this is your guy.

2. Aero Precision M4E1 Uppers - Best Mid-Tier Uppers

Best Mid-Tier Uppers

Aero Precision M4E1 .300 BLK Uppers

$419

at OpticsPlanet

Prices accurate at time of writing

$419 at OpticsPlanet

Brownells (see price)

Aero Precision is one of the best companies out there for reasonably priced, modern, high-quality AR components. 

The M4E1 in .300 BLK comes available in 8, 10, and 16-inch barreled options.

A 10-inch barrel on an AR pistol or a short-barreled rifle is perfect for the .300 BLK. The uppers all feature different-length handguards that accommodate the mounted flash suppressor.

Keep in mind that most of the time, these uppers do not come with a bolt-carrier group or charging handle. Be sure to figure those into the cost when pricing out your next build.

Aero makes gear that works, and these uppers are perfect for your next .300 BLK build or to convert your 5.56 rifle. Be sure to check out our review of their 5.56 uppers.

3. Palmetto State Armory - Most Affordable Uppers

Most Affordable

PSA .300 Blackout Uppers

$169

at Palmetto State Armory

Prices accurate at time of writing

$169 at Palmetto State Armory

PSA makes a huge range of items for the AR platform. They are known for being extremely budget-friendly and restocking their items regularly so that you aren't left waiting months to get what you want.

One of the many things they produce is .300 BLK in uppers of various sizes, from 7.5-inch barrels all the way to 16-inch barrels, with every standard size in between.

Want to build a short little pistol? Check. SBR? Check. Rifle? Check. No matter what kind of .300 BLK build you want to create, you can likely find a suitable upper for it from PSA.

These aren't premium options, but they are well-priced and offer good features. They also have competitively priced complete lowers and fully assembled .300 BLK gun options as well.

4. Radian Model 1 - Best Overall Upper

Best Overall

Radian Model 1 .300 BLK Complete Upper

$1829

at Midway USA

Prices accurate at time of writing

$1829 at Midway USA

OpticsPlanet (see price)

Palmetto State Armory (see price)

If you are looking for the best of the best, look no further than the Radian Model 1.

These uppers are made with ultra-high-quality raw materials and constructed with exacting quality control.

Features include a premium match-grade 416R stainless barrel, nitrided enhanced M16 BCG, Radian Raptor SD suppressor-optimized charging handle, Radian handguard with anti-rotation pins, and your choice of SilencerCo ASR or Dead Air flash hider.

Radian also guarantees sub-MOA performance when using Black Hills match-grade ammo. If you want the best of the best, Radian sits atop the mountain.

While this upper is spendy, the performance and build quality may be enough to justify the cost for some.

5. Brownells BRN-180 Gen 2 - Short-Stroke Piston Option

Short-Stroke Piston Option

BRN-180 Gen 3 .300 BLK Upper 9″

$1199

at Brownells

Prices accurate at time of writing

$1199 at Brownells

Want something a little different? Enter the Brownells BRN-180 series, which is based on the AR-180 rifles of old that didn't have a buffer tube, but instead used a short-stroke piston.

That means if you went with an under 16-inch barrel (which you pretty much gotta do with a .300 BLK), then you can get a folding brace for a super compact AR.

My choice is the 10-inch .300 BLK upper that we built for a super nice truck gun.

Brownells also now offers a suppressor-optimized version that includes a gas shut-off setting. Combined with an adjustable side-charging handle that can be pivoted downward, this allows you to seamlessly switch between semi-auto and a true "single-shot" bolt-action mode for extreme sound control.

To make the most of the bufferless design, we recommend pairing it with a lower that has a 1913 rail at the rear instead of a provision for a buffer tube. American Defense Manufacturing makes an excellent ambi lower that is meant to be paired with the BRN-180.

ADM UIC-180 Stripped Ambidextrous Lower Receiver

$342

at Brownells

Prices accurate at time of writing

$342 at Brownells

Check out our full review of the 16-inch 5.56 version.

Why You May Want a .300 Blackout Upper

The .300 BLK became a behemoth in the industry because of its direct compatibility with existing AR-15 rifles.

This includes compatibility with standard 5.56 magazines, bolt carrier groups, upper and lower receivers, rails, buffers, buffer assemblies, stocks, etc. Really, the biggest change is the barrel and the gas system.

Besides the easy conversion between 5.56 and .300 BLK, the .300 BLK does a lot the 5.56 can’t.

First off, it’s a very versatile load with projectiles weights ranging from 110 grains to 220 grains. The 110-grain rounds are supersonic, and the 220 subsonic.

A subsonic round is much easier to suppress and much quieter when suppressed. The .300 BLK also reaches peak ballistic potential from a 9-inch barrel.

The 5.56 requires a 20-inch barrel to reach peak ballistic performance.

I won’t dive too deep into the 5.56 vs. .300 Blackout debate because we have an article on that.

In my opinion, the two rounds are designed for different tasks, and having both simply opens up your options.

What I will do is point you to a few of the best .300 BLK upper receivers so that you can make your transition to this wonder round.

Best .300 Blackout Barrel Length?

This question comes up a lot...and the answer varies depending on your end use and if you're using a suppressor.

We asked Clint Hanson, the founder of Ballistic Advantage, and his go-to barrel length is 10 inches for reliability.

The 10.3-inch length is "not too short and not too long from an all-around/fit every human size standpoint" because you have to figure in the handguard and potential suppressor length.

Once you go under 8 inches or so, you can run into cycling issues since the .300 BLK is a low-pressure round.

So if compactness is the name of the game...make sure you have a suppressor to add some backpressure and also enable you to run a longer handguard.

"Every length has a problem it’s solving, but the 10.3 inch is the go-to and most versatile."

.300 Blackout Safety

I do want to note one thing before you run out and get a new .300 BLK upper, you NEED to be careful when switching between uppers or even when you have a dedicated .300 BLK rifle and a 5.56 rifle. 

You see, .300 BLK can chamber in most 5.56 barrels; however, if you try to shoot it, your barrel (and sometimes more) will literally burst. 

As you can see in the image above, bad things can happen when you load the wrong cartridge into your rifle. Make sure you keep ammo and mags separate.

Personally, I keep them organized by using different color mags - FDE and black for 5.56 and Olive Drab for .300 BLK. I also double and triple-check things before loading a mag into the rifle.

Meet the Experts

This article was put together by Pew Pew Tactical CEO and Founder Eric Hung. In addition to founding Pew Pew Tactical as a place for shooters to learn, he’s also an NRA-certified pistol instructor and a USPSA/3-Gun/NRL22 competitor. Eric has also researched and written over 250 articles on firearms, training, gear, and just about everything else related to firearms.

Editor-in-Chief Jacki Billings runs our experienced team of reviewers. She is a member of the Society of Professional Journalists, ACES: Society for Editing, and the Professional Outdoor Media Association. Additionally, she is an NRA-certified Pistol Instructor and former Concealed Carry Instructor. Jacki has a bachelor’s degree in journalism and has worked as a media professional for close to 20 years, specializing in gun media for almost 10 years. She uses her professional journalism and editing experience to set testing protocols and editorial standards for Pew Pew Tactical.

Also editing this article is Wyatt Sloan, Editor. Wyatt is an NRA and USCCA-certified instructor with previous experience as a competitive shooter. Wyatt personally owns over 200 firearms and has 10 years of home-based FFL firearm sales. He has used his extensive experience with firearms at large to test guns for Pew Pew Tactical — evaluating them based on our standards and metrics.

Final Thoughts

With suppressors and SBRs being all the rage, the .300 BLK continues to grow. The ammo price continues to drop, and upper receiver options are everywhere.

These are just my favorites and represent a very small section of the market. I’m one man and couldn’t possibly see each and every upper out there. Knowing the industry, there must be some amazing options on the market I simply haven’t seen. 

What are your favorite .300 BLK upper receivers? Anything that makes them stand out? Need a dedicated optic for the .300 BLK drops? Check out our Best .300 BLK Scopes & Optics.

Latest Updates

• June 2025: Removed Ballistic Advantage complete uppers (discontinued), added PWS MK109 MOD 1-M upper. Updated Brownells BRN-180 to reflect the new Gen 3 version and added ADM UIC-180 lower.
• February 2024: Replaced Radical Firearms upper with Radian Model 1. Updated BRN-180 upper to reflect Gen 2 changes.