What's the best barrel length for 300 BLK? That's an excellent question. A versatile and well-liked cartridge, the 300 Blackout cartridge is also known as the 300 AAC Blackout or 7.62x35mm. It is extremely well suited for hunting, home defense, and suppressed shooting (particularly, of course, with subsonic ammunition). The performance of the 300 Blackout round depends significantly on the length of the barrel. In the post below, Faxon Firearms helps us explore the benefits and drawbacks of various 300BLK barrel specs.
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300BLK Barrel Selection: Things to Know
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The main question you need to ask yourself is whether you plan to use a suppressor. This should definitely be a consideration, given the advantages 300 blackout ammo offers with a subsonic load, but there are 300 BLK supersonic loads as well. Then look at legalities like NFA since the AR pistol + (short) pistol length barrel + pistol brace combo (vs SBR) is an on-again, off-again proposition.
You'll also want to take the weapon's intended use into account. The best barrel length for hunting might not be optimal for someone fighting at bad breath distance.
The 300BLK cartridge does not react to a longer barrel like other cartridges (such as the 22lr); .22 rounds gain speed through longer barrels. For instance, a shorter barrel shooting 300BLK will perform better (for that caliber) than 5.56mm, though it will heat up faster.
There are many 300BLK shooters who say a 9" 300 BLK barrel is the “sweet spot” for subsonic velocity cartridges, but you can go even shorter (like the Faxon Firearms 7.5" or Ballistic Advantage 6").
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7.5 inch Faxon barrel in 300BLK
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How Much Does Barrel Length Affect .300 Blackout Velocity?
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Faxon Firearms advises that based on their personal experience and research, the 9″ 300 BLK barrel is the best overall barrel length with or without a suppressor, especially since an 8″ barrel is the minimum warranty barrel length for many suppressor manufacturers.
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Best 300 Blackout Barrel Length: Home Defense
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The .300 Blackout round is an excellent choice for home defense as it combines power, efficiency, and lethality even when fired from a short-barreled rifle.
A short-barreled rifle is ideal for home defense as its compactness makes it easier to maneuver throughout the home. Despite its compact size, a .300 BLK round fired from a short barrel can still hit targets up to 100 yards away.
For optimal home defense with the .300 Blackout, Faxon Firearms recommends a barrel length of at least 6″ to 8″.
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10.5 inch Faxon barrel in 300BLK
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Best 300 Blackout Barrel Length: Hunting
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The ideal barrel length when hunting with .300 Blackout is one able to reach long-range targets with sufficient bullet velocity and energy on target for a lethal impact.
Longer barrel lengths offer greater accuracy and velocity, with a maximum length of 16″ for the .300 Blackout. This length ensures complete gunpowder combustion to generate maximum force and stabilizes the bullet for a flatter trajectory and improved accuracy.
Additionally, a 16″ barrel offers a long line of sight for better aim, making it the recommended choice for long-range hunting.
Faxon Firearms 16" barrel in 300BLK...
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Choosing the right barrel length for the .300 BLK Can Be Hard
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At 10″, the muzzle velocity has not yet reached its peak. A heavy subsonic round in a 10″ barrel may have lower velocities but allows for the use of a suppressor without damaging your hearing. Ammo hitting supersonic velocity out of a 10″ barrel retains rifle caliber velocities but with more significant bullet drop at longer distances (this will vary depending on bullet weight).
At 16″, muzzle velocities are near their maximum. As a result, heavy-grain subsonic bullets struggle to retain their subsonic terminal performance, while supersonic ammo has increased effective range and reduced bullet drop. The 16″ barrel also provides greater energy upon impact, regardless of ammo type.
Faxon Firearms .300 BLK Gas Adjuster Knob on the ARAK-21 Upper Receiver. Your first 300 BLK build probably shouldn't have an adjustable gas block, but once you get used to things it could be an interesting option to explore. Photo by Zero7one.
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The barrel twist rate also impacts performance and should be considered when selecting optimal barrel length and determining the effective range of the .300 Blackout. For example, a 1:8 twist is best for lightweight supersonic rounds, while the 1:7 twist is recommended for heavy subsonic ammo with a suppressor.
These are a few of factors to consider when selecting the ideal barrel length for the .300 BLK rifle and determining its effective range -don't just go buy one. Do some research, ask some questions, and make sure you have the one you need.
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Faxon Firearms 16" barrel in 300BLK...
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Several manufacturers have produced barrels and complete rifles in 300 Blackout: some of those include Advanced Armament Corporation, Mega Arms, Radical Defense, Modern Materiel, Q, SIG Sauer, and many more.
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Some of the best 300 blackout barrels come from:
Ballistic Advantage (check out their Modern Series barrel options)
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