If you’re assembling a new .300 Blackout AR-15 from scratch without using a ready-made upper receiver; you must pick the right barrel. The purpose of .300 AAC Blackout changes depending on whether it is loaded to supersonic or subsonic velocities. Choosing the right barrel largely rests on the type of ammunition you intend to fire regularly.
Best .300 Blackout Barrels
1. TRYBE Defense 16” Blackout Government Profile AR Barrel
If you’re building your first AR-15 in .300 Blackout, the TRYBE Defense 16” Blackout Government Profile Barrel is an excellent choice.
This affordable 16” barrel is ideal for low-cost carbine-length AR-15 builds. It meets the legal requirements for installation on a rifle, allowing you to use a shoulder stock.
This barrel also features a carbine-length gas system and a 1:8 twist rate, making it ideal for use with supersonic ammunition. With the right choice of ammo, an AR-15 fitted with this barrel can be used for hunting or even home defense.
Durability is not an issue with this barrel, because it is made from 4150 chrome-moly vanadium steel, coated with a standard nitride finish. Although no muzzle device comes with this barrel, you will find a standard 5/8×24 thread pitch on which you can install the flash hider, muzzle brake, or suppressor of your choice.
2. Wilson Combat Match Grade Barrel 300 AAC Blackout
Shooters looking for the best accuracy out of a .300 Blackout AR-15 may be interested in the Wilson Combat Match-Grade Barrel, recognizable with its distinctive bead-blasted stainless steel finish and Wilson Combat logo engraved near the muzzle.
This 416R stainless steel barrel is 16” long. It features a 1:7 right-hand twist rate, capable of adequately stabilizing most factory supersonic bullets and most subsonic projectiles, up to 250 grains.
This barrel features 6-grooved precision button rifling, a high-quality muzzle crown, and tight manufacturing tolerances, making it one of the most accurate .300 Blackout barrels available on the market today.
With high-quality match-grade ammunition, you can expect an accuracy of 1 MOA or better. It’s an ideal barrel for hunting or close- to medium-range competition shooting builds.
3. Spikes Tactical Lothar Walther 10” Stainless Steel Barrel
Spikes Tactical makes some of the finest AR-15s and AR-15 parts. If you want to introduce the Spike’s quality to your AR-15 pistol or SBR build, you can’t go wrong with the 10” barrel, manufactured from a high-quality Lothar Walther blank.
Spike’s uses a proprietary chrome-moly vanadium steel alloy called DIN 21CrM0V511, which was first developed by FN Herstal for the production of M249 light machine gun barrels. You can expect exceptional durability and reliability from this barrel; it will last you a lifetime.
This barrel is chrome-lined and phosphate-coated according to mil-spec standards. It features a 1:7 twist rate, ideal for stabilizing subsonic projectiles, and a standard 5/8×24 thread pitch, which accepts most .30-caliber muzzle devices.
4. Rosco Manufacturing Purebred Heavy Profile 8.2” .300 BLK
Rosco Manufacturing is a lesser-known manufacturer based in Rhode Island, but its products compete with the best from the established brands. All its raw materials are sourced from the United States, ensuring that the barrel is made in the USA from start to finish.
AR-15 parts such as the Rosco Purebred Heavy Profile .300 Blackout barrels are among the finest available on the market. This barrel can produce high accuracy out of the box, with no additional work or gunsmithing.
Rosco manufactures the Purebred barrels entirely in-house, using 416R stainless steel blanks as a starting point. This barrel is precision button-rifled, micro-polished, and finished with a corrosion-resistant nickel-boron finish. Nickel-boron is a strong alloy made of 95% nickel and 5% boron. The resulting barrel is highly durable and low-maintenance.
The 8.2” barrel length and 1:8 twist rate are ideal for suppressed subcarbines, SBR builds, and AR pistols. It is excellent for use with a suppressor because it offers one of the shortest lengths possible without compromising ballistic performance, keeping your firearm handy and maneuverable.
5. Noveske Lo-Pro Gas Block .300 AAC Blackout 12.5 inch
Noveske is a name synonymous with uncompromising quality, offering a wide selection of innovative, high-quality parts for AR-15s.
The Lo-Pro Gas Block .300 AAC Blackout barrel is tuned explicitly for suppressed use. Noveske guarantees bolts hold open on the last round if used with 208-grain or 220-grain ammunition and a suppressor. Recommended suppressors include the AAC 762-SDN-6 and the Surefire 762K.
As the name suggests, this barrel is fitted with a low-profile gas block, allowing the user to install a long tube handguard.
Like most Noveske barrels, the barrel is manufactured from 416R stainless steel, pre-hardened to a Rockwell HRC rating of 30 before machining, guaranteeing superior durability.
The 12.5” barrel length ensures maximum performance in short-barreled platforms such as AR pistols, SBRs, and subcarbines. Optimal performance is guaranteed if you run the barrel unsuppressed with supersonic ammo or suppressed with subsonics.
Differences Between Supersonic and Subsonic
Supersonic .300 Blackout ammunition replicates the ballistics of 7.62x39mm, used by classic AK pattern rifles, but with cartridge dimensions designed with the AR-15 magazine in mind.
Shooting supersonic .300 Blackout ammo gives your AR-15 the appeal and firepower you expect of an intermediate .30 caliber firearm.
When fired through a 16-inch carbine-length barrel, a typical 125-grain .300 Blackout FMJ bullet exits the muzzle at velocities ranging between 2,150 and 2,250 feet per second. This gives it a muzzle energy equivalent to that of an AK-47 shooting a 123-grain bullet.
Against a human-sized target, it has roughly the same effective range of about 300 to 400 yards. However, if you use it for hunting deer or hogs, stay within 100-150 yards at most, just as you would with a .30-30.
In contrast, subsonic .300 Blackout ammunition provides a better and more powerful alternative to subsonic 5.56mm or pistol cartridges, similar to the Russian 9x39mm cartridge.
Subsonic ammunition uses long, heavy bullets and a reduced powder charge. The muzzle velocity remains below the speed of sound, eliminating the loud crack that usually occurs with supersonic ammo.
Using a suppressor helps preserve your hearing, avoid noise complaints, improve your situational awareness, and reduces flinching.
If you use a suppressor on a firearm shooting subsonic ammunition, it suppresses most of the generated noise, so you don’t need hearing protection.
The tradeoff for using subsonic ammo is that since the projectiles are heavier and travel at a lower velocity, they drop faster. A typical 190-grain subsonic bullet drops 4” at 100 yards, approximately 30” (2.5’) at 200 yards, and about 96” (8’) at 300 yards. This significant bullet drop means your subsonic .300 Blackout’s effective range should remain within 100 yards.
There are 2 major categories of barrel lengths for .300 Blackout builds: Carbine-length barrels (almost always 16”) and pistol-length barrels (ranging between 6.5” and 12.5”).
Most factory ammunition, both supersonic and subsonic, contains a powder charge that completely burns in a barrel between 9-10” long. There is no need for a .300 Blackout firearm to have a barrel longer than 10.5”. Longer barrels provide minimal muzzle velocity, but they add weight. Some weight can be beneficial to combat recoil, but a rifle that is too heavy is cumbersome.
If you want to own an AR-15 rifle chambered in .300 Blackout legally, the minimum barrel length is 16”.
If the barrel is smaller than this, Federal Law considers the firearm a Short Barreled Rifle (SBR), which is illegal to own without paperwork and approval from the ATF.
A great alternative is an AR-15 pistol. The ATF considers an AR-15 to be a pistol if it has a barrel length under 16” and no stock, leaving only a protruding buffer tube.
It is possible to use a shorter barrel length on an AR-15 pistol. It is also legal to install a stabilizing arm brace; a device mounted on the buffer tube that straps around your forearm to help you shoot more accurately.
With proper paperwork and approval from the ATF, you can also look into manufacturing an SBR, which allows you to use an appropriate shoulder stock on barrels under 16” long. However, this option is relatively costly ($200 tax stamp) and involves a waiting period.
A rifled barrel is machined with twisting grooves and lands. These impart spin to the bullet, providing it with spin stabilization, which allows it to fire accurately at relatively long distances. The twist rate is the distance needed for the rifling to complete a full revolution. For example, a twist rate of 1:7 means 1 complete revolution in 7”.
Different twist rates provide varying stabilization levels. You must pair the right bullet weight with your barrel’s twist rate to provide your bullets with the correct amount of spin stabilization. Too much, and the bullet will suffer from over-stabilization; too little, and it will tumble.
- Over-stabilization occurs when the twist rate is too fast, imparting too much spin on the bullet and causing it to fly nose high. Over-stabilization reduces accuracy and may cause specific bullet designs to fail.
- Tumbling or insufficient stabilization occurs when the twist rate is too slow. Without sufficient spin, the bullet yaws and tumbles, significantly reducing accuracy and effectiveness. The term keyholing refers to the effect of a tumbling bullet striking a paper or cardboard target, which leaves holes resembling keyholes.
In .300 Blackout barrels, the vast majority of twist rates available on the market today are 1:7 and 1:8. Either can stabilize supersonic bullets adequately.
If you intend to shoot subsonic ammunition between 210 to 245 grains, a1:7 twist rate offers better stabilization.
The Last Word
Regardless of the barrel you choose for your .300 Blackout AR-15, build your firearm according to your intended purposes and the ammunition you want to shoot. If you plan to use your firearm for hunting, self- or home-defense, or competition shooting, you want a barrel that improves your handling, maneuvering and doesn’t add too much weight.
Even if you can use standard AR-15 magazines to load .300 Blackout, use parts with clear .300 Blackout markings on your magazines and gun parts. Marking your gun parts helps reduce the risk of chambering ammunition with the wrong caliber.