Building your very own AR platform for a .300 Blackout is an excellent way to customize your very own shooting experience. The popularity of this cartridge has grown in recent years for match shooting and hunting and offers some fun shooting scenarios since it adapts well to both subs subsonic and supersonic options, especially when suppressed.
If you are looking for hard-hitting accuracy, and want total control over the rifle platform, then here’s our list of the 5 Best 300 Blackout Uppers!
Comparison Table of The 5 Best .300 Blackout Upper Receivers
BRAND
APF 300 BLK Carbine Complete Upper Receiver
DETAILS
- 16 inch barrel
- 1:8 Twist
- Carbine Length Gas System
- M-LOK Handguard
Primary Weapons – MK109 Pro Upper Receiver Complete 300 Blackout
- 9.75 inch barrel
- 1:8 twist
- Adjustable gas system
- M-LOK Handguard
Aero Precision – M4E1 Assembled Upper Receiver .300 Blackout Black
- 8, 10, or 16 inch barrel
- 1:8 twist
- Pistol length gas system
- M-LOK handguard
PSA 10.5″ Pistol-length 300aac 1/8 Phosphate 9″ Lightweight M-LOK Upper
- 10.5 inch barrel
- 1:8 twist
- Pistol length gas system
- M-LOK handguard
Stag Arms – Stag 15 300 Blackout 16in Upper Receivers
- 16 inch barrel
- 1:7 twist
- Pistol length gas system
- M-LOK handguard
Upper Receivers: Essential AR Types
If you have never actually built an AR before, you might not be aware of the different AR-15 receiver types you need to know about before picking one. In order to truly understand the part, you need to understand what it actually does since all the essential AR15 parts, minus the shooting mechanism, are part of the upper.
Upper receiver types are broken into military classifications that are specific to mil-spec distinction for each of the M16/M4 model setups. Although there is a history and quite a bit of detail behind each, what it all comes down to for civilian use is whether a fixed carrying handle and/or forward assist is present. Most uppers for civilian use are an A4 option with various handguard and barrel choices for your own needs. However, understanding these differences is important when you begin getting into the details of what you are looking at.
A1 Upper
The A1 is the original AR15 upper design installed on the M16 A1 rifles during Vietnam. It was a lightweight option with a forward assist and fixed carry handle. The barrel offered a 1:12 twist for accurate firing within 450 yards.
A2 Upper
The A2 served as an upgraded version of the A1 with a fixed carry handle and forward assist. The rear sight was more advanced and adjustable for elevation compared to the A1 to provide more accuracy at longer distances. It also had a heavier barrel and twist rate in either a 1:7 or 1:9 twist rate.
A3 Upper
The A3 is defined by a flat top configuration with a detachable carrying handle equipped with a Picatinny or Weaver rail for accessory mounting purposes. It also includes a forward assist and rifle cuts in the feed ramp. Some of these may also provide a higher scope positioning due to an upwards base extension.
A4 Upper
The A4 is most commonly seen in modern civilian AR platforms and provides a very similar design to the A3 with a flat top upper receiver. The main difference is the A4 includes A4-style feed ramps.
Upper Receiver Group Key Components
The main components of an assembled upper receiver consist of the barrel, handguard, gas block and tube, bolt carrier group, and charging handle. It attaches to your lower receiver group to form a fully functional firearm. As with the rest of your AR-15 uppers, you can customize your gun to your own personalized needs. Either purchase a complete upper, or by the parts for a DIY build.
Gas Block and Tube
A gas pressure system is required to properly fire, eject, and chamber a new round. There are four gas system lengths: rifle, mid, carbine, and pistol length. The 300 BLK is generally found as a pistol length or carbine length with a 16-inch barrel, although the pistol-length gas system will work for up to a 16 inch without issue.
Bolt Carrier Group
The bolt carrier group includes the firing pin, bolt, cam pin, and gas key. This is the part responsible for loading, firing, and ejecting properly. These come both pre-assembled or you can piece it together for a more customized fit.
Charging Handle
The charging handle pulls the bolt carrier group back to chamber a round. It allows you to eject a faulty shell to reload as well. It also allows you to load the first round of a new magazine when the bolt is closed.
Forward Assist
The forward assist is an addition to the upper receiver to provide enhanced reliability. It works to ensure the bolt goes all the way back to the battery. Even though it may not truly be a completely necessary component, it does provide dependability.
Ejection Port Cover
The ejection port cover is designed to help keep environmental elements from the inside of your rifle. It opens when the bolt carrier group moves to the back and allows the ejection of the spent cartridge.
Barrel
The barrel is truly the most important part of the AR-15 upper receiver. Without it, all the other parts aren’t going to be doing much since this is what the bullet passes through. The 300 Blackout barrel is popular in both pistol-length and carbine-length options – measuring between 10.5-inch barrel and 16-inch barrel length
Rail System/Handguard
Barrels get very hot, very quickly after firing round after round. Since AR platforms are designed to provide accuracy after thousands of rounds are fired through them, handguards provide protection for both the barrel and your hand when firing. Most of these are a free-floating handguard style to provide easy modification and offer a rail system to use with accessories such as optics, various sights – such as iron sights or backup sights, or even flashlights and grips.
What to Watch For: A Quick Buyer’s Guide
There are quite a few variations in relation to what is labeled as an AR-15 rifle upper for use with the 300 BLK cartridge. Because of this, you want to pay attention to a few particular terms and features being offered when narrowing down your choices.
AR-15 rifle upper receivers are sold either as complete builds or kits, both as stripped or barreled options. A stripped upper is the basic frame, per se, and has no added parts installed. It is part of your option when piecing together a build, or prefer an aftermarket replacement part.
A complete, barreled upper includes the barrel, gas tube, handguard, and ejection port installed. Purchase as a complete build or as a kit to piece together on your own. Often kits require you to also purchase some additional parts, such as charging handles but are excellent choices for when you want a fully customized option.
Materials
Most receivers of any type are made from 6061-T6 aluminum or 7075-T6 aluminum, a durable, long-lasting option that can handle the pressures you place them under when firing your rifle. They are also made from one of three different processes: cast, billet, or forged. These are often also coated for corrosion resistance and may offer various solutions for durability.
Cast
Cast receives are made through the process of die-casting when molten aluminum is poured into molds. This is inexpensive and helps keep overall costs down for civilian-approved rifles.
Billet
A billet upper receiver has been CNC-milled from a solid piece of aluminum. It is more expensive than casting but still provides affordability without adding extra weight.
Forged
Forged receivers are generally the most expensive option and are created by hammering into shape from a single piece of aluminum. These offer the highest quality in terms of strength and density.
Thread Pitch and Twist Rate
A .300 BLK barrel almost all have a ⅝-24 thread pitch to provide excellent compatibility with most muzzle devices, such as a muzzle brake or A2 flash hider. This is a standard threaded barrel choice for a .30-caliber bullet and usually offers a 1:7 or 1:8 twist rate to stabilize heavier subsonic ammunition or supersonic ammunition respectively.
Handguard and Rail Systems
A BLK upper assembly will offer a handguard and rail system of some sort for accessory addition. These are almost always M_LOK compatible and are a Picatinny rail or Weaver rail. This can vary from upper to upper and is easy to customize with aftermarket options as well, allowing you to include a full-length rail or something short depending on your needs.
Compatibility
In order to complete your build, you need a compatible lower. Of course, you can always piece together your own, but to look for manufacturing specs to help point you in the correct directions in reference to fit.
300 Blackout Lower Receivers Worth Taking a Closer Look At
1. APF 300 BLK Carbine Complete Upper Receiver
- 16 inch barrel
- 1:8 Twist
- Carbine Length Gas System
- M-LOK Handguard
Alex Pro Firearms, or APF, is an Alexandria, Minnesota-based company that offers serious firearm quality and is made right here in the U.S. of A. All parts are designed and built in-house, allowing you to pick and choose from complete builds, or the parts you need to customize your own. The APF 300 BLK Carbine Complete Upper provides a “Pro” experience at a fair price.
The 16 inch, 1:8 twist 4140 chrome moly steel medium contour barrel is backed by a carbine-length gas system housed in a forged aluminum receiver for superior quality and durability. The in-house 12.5-inch free-floating M-Lok handguard is lightweight and easy to remove for customization and offers the rail system you need to accessorize. With an M16 bolt carrier nickel boron coating, standard charging handle, and A2 flash suppressor, you have everything you need to complete your build with a long-lasting product.
Pros
- Inhouse builds to pick and choose parts
- Carbine length gas system to handle various options
- Complete build
Cons
- Pretty much the perfect option, which isn’t a con at all!
2. Primary Weapons – MK109 Pro Upper Receiver Complete 300 Blackout
- 9.75 inch barrel
- 1:8 twist
- Adjustable gas system
- M-LOK Handguard
Primary Weapons Systems offer a unique, long-stroke, gas-piston design that is amongst the most innovative in the current firearm industry. The PWS MK109 PRO upper receiver is a complete 300 Blackout build that provides everything you need to complete your customized AR-15 set-up.
Included is the complete bolt-carrier group with a Radian Weapons Raptor charging handle to provide an overall length of 18.5 inches with a pistol length of 9.75-inch barrel. The 1:8 twist is powered by an adjustable gas system if you decide on changing out your barrel lengths at any time, and a free-float, M-LOK handguard finishes off the all-black look.
Pros
- Innovative, long-stroke piston design
- Complete build
- Adjustable gas block system
Cons
- Does require some knowledge of adjustments and working of the system – which isn’t at all a con!
3. Aero Precision – M4E1 Assembled Upper Receiver .300 Blackout Black
- 8, 10, or 16 inch barrel
- 1:8 twist
- Pistol length gas system
- M-LOK handguard
Aero Precision has long been known as a firearm manufacturer that delivers what their customers need, and the Aero Precision uppers are quality picks. The M4E1 assembled receiver chambered for the 300 Blackout provides a custom pistol/SBR/Carbine build with your choice of an 8 inch, 10-inch, or 16-inch carbine length chrome-moly barrel. The look is completed with an M-LOK EM-7 7 inch handguard for the 8-inch barrel, 9 inches for the 10-inch barrel, and 15 inches for the 16-inch barrel.
The pistol-length gas system offers a low-profile gas block and is more than enough power for your shooting needs. The barrel is complete with a standard A2 flash hider on the threaded end for easy customization. To help you further customize your build, the bolt carrier group and the charging handle is not included so you can pick and choose what is best for you.
Pros
- Multiple barrel options available
- Custom feel and choices for your build
- Low profile gas block
Cons
- Does not include the bolt carrier group or charging handle
4. PSA 10.5″ Pistol-length 300aac 1/8 Phosphate 9″ Lightweight M-LOK Upper
- 10.5 inch barrel
- 1:8 twist
- Pistol length gas system
- M-LOK handguard
Palmetto State Armory is known for its affordable in-house builds created for quality durability and customer satisfaction. Their forged 7075-T6 A3 AR Upper chambered for a 300 AAC Blackout is made to MIL-SPECS and has a hard coat anodized black finish. The 10.5-inch chrome moly vanadium steel barrel provides a 1:8 inch twist rate and is finished off with the PSA 9 inch lightweight M-LOK, free-float rail for all your accessory needs. An A2-style flash hider is also included.
A MIL-SPEC bolt carrier profile offers full-auto capabilities and is made from shot-peened Carpenter 158 steel with a parkerized outer and chrome lined inside. The charging handle is included.
Pros
- Patented PSA build
- Dependable pistol length barrel
- Flawless use
Cons
- Best used with a PSA lower and might not fit other manufacturer lowers
5. Stag Arms – Stag 15 300 Blackout 16in Upper Receivers
- 16 inch barrel
- 1:7 twist
- Pistol length gas system
- M-LOK handguard
Stag Arms offers the Stag 15, a 300 Blackout, 16 inch AR-15 upper receiver that provides a hard-hitting option in a full-length design that boasts a 16-inch barrel complete with a 1:7 inch twist rate. The big-bore, .30 caliber barrel provides amazing velocity and trajectory all in an easy to manage package suited for a huge array of shooters. It does not come with the bolt carrier group and charging handle.
Finished with a QPQ-nitride-finished coating, this is a durable, quality choice that will keep you shooting round after round without issue. A classic birdcage-style flash hider helps finish off the look when combined with an ergonomic Stag Slimline handguard, complete with M-LOK attachments slots. As a bonus, it also comes in a left-hand shooting style for those who prefer not to adjust!
Pros
- Offers both right and left-handed options
- Big-bore .30 caliber barrel
- Birdcage-style flash hider included
Cons
- Does not come with a bolt carrier group or charging handle
Conclusion
No matter whether you want to shoot subsonic ammo or supersonic ammo, the 300 BLK is a versatile AR 15 build that works well with both rifle length and pistol length barrels and compatible gas block systems. When choosing an upper for your build, be sure to consider all the components to ensure you receive what you need. It also is important to look for lower receiver compatibility.
We’d love to hear of your favorite AR build products and have the chance to answer any questions about our top picks. These are all solid choices that provide more than adequate performance – making them a popular choice among shooting enthusiasts. As always, please share!