.300 Blackout Guide: Best Barrel Length, Build Tips & More thumbnail image

.300 Blackout Guide: Best Barrel Length, Build Tips & More

Feb 17th 2021

History of the .300 Blackout

Developed in 2009 by the Advanced Armament Corporation or AAC, the .300 Blackout is regarded as a round that gives top-class performance when compared to similar calibers. The development of the .300 Blackout was a joint effort between AAC and Remington Defense, and this was to produce a replacement for the 5.56 NATO.

With the War on Terror on the rise at the time, the development was also motivated by the need to produce a .30 caliber cartridge that would produce better results in combat than the 5.56mm rounds that were currently in use. Avoiding the logistical nightmare that would have been to replace the military's standard issue rifle during an ongoing war, the .300 Blackout was designed to be compatible with the M4 system. This adaptability to the existing rifle specifications was made possible by the fact that the designers and engineers chose not to go down the path of building up from scratch. Instead, they built the round from the M4-compatible 5.56mm cartridge.

The .300 Blackout Specs That Make It Worth Your While

The .300 AAC Blackout is designed as a variation of the older .300 Whisper ammunition. Compared to other bullets, a .300 Blackout is a 30-caliber bullet in a .223/5.56mm shell casing. The distinction means the round can fit into an AR magazine, an AR upper built for the .300 Blackout, and an AR lower. This means that one gun can serve as two just by switching the uppers.

Built for use with suppressors but still maintaining subsonic speeds, the .300 Blackout is designed to penetrate heavy barriers while still maintaining an overall manageable weight profile. With a relatively convenient recoil, the .300 AAC Blackout is known for giving users an easier time staying on target. It gives an almost negligible muzzle rise while shooting, meaning most of the energy produced during recoil comes back to the shooter's shoulders. Though the muzzle rise and recoil forces are not entirely negligible, they are not enough to affect follow-up shots for the shooter.

Standardized with SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) specs means every design aspect of the .300 Blackout is kept similar, regardless of the manufacturer.

Ballistically, the .300 AAC Blackout has almost 17% more energy at 300 meters than the 7.62 x 39 round. This is because the latter is thicker and wider, causing more drag as a projectile. Compared with the muzzle energy of the .556, the .300 Blackout has the same muzzle energy that the .556 has at 500 meters while it is at 700 meters. This means the .300 Blackout is more effective at long distances.

The 220 grain subsonic .300 Blackout goes at about 1010 feet per second with 500 foot-pounds of muzzle energy. This makes the .300 Blackout an effective, versatile, and reliable close combat round. The .300 Blackout also comes in a supersonic variant, which means once fired, the bullet travels faster than the sound barrier. This high-speed feature means that the bullet will spend relatively less time in motion and thus less prone to the effects of elements like the wind.

The .300 Blackout is a worthy firearm since it gives you the ballistic power of an AK just by switching the upper in an AR. This compatibility means that it can allow for major savings if you're a gun enthusiast who likes to stay on a budget.

Do Special Forces Use the .300 Blackout?

As a testament to the efficiency of the .300 AAC Blackout, several military units across the world, including the Netherlands, United Kingdom, and the United States, have adopted it. This is because most operators commend the high stopping power of the 300 Blackout in close-combat engagements compared to other ammunition issues.

Can a .300 Blackout Barrel Shoot 556?

Even though the .300 AAC Blackout's design implementation was based on the shell casing of the .556, the latter cannot be shot from the barrel of a .300 Blackout.

How Does the 350 Legend Compare to the .300 Blackout?

Compared to other ammunition like the 350 Legend, the .300 AAC Blackout is more effective in taking long-range shots. It also has a great barrel life, which means it can go for long periods and operate effectively under varying conditions. The .300 Blackout's rather streamlined shape allows for it to have magazines with minimal curvature, which makes them less prone to jam.

Barrel Lengths That Work for the AAC .300 Blackout

Though there is a lot of talk among gun enthusiasts about the nine-inch sweet spot of barrel length when it comes to the .300 Blackout, the ammo works well with different variations of barrel lengths and uppers. Without unnecessary weight and length implications, the gun barrel's length is used to produce room for the gun powder in your ammo to burn out before the bullet exits. A longer barrel, because of its increased surface area, provides more room for cooling in instances where you shoot continuously.

Having a longer or shorter barrel is a matter of understanding the dynamics of ammunition, barrel design, and overall shooting conditions before you settle on a preference. For instance, having a relatively long barrel has the gases from the already burned-out gunpowder trapped for longer, which means there will be more push time of the bullet by the gases. The shorter a gun barrel, the more the gas expulsion at the muzzle equals a relatively louder sound every time you shoot. To counter this, of course, there is always the option of sticking a silencer onto the muzzle. In instances where that is not an option, however, you can always go long or brace yourself for those loud blasts with every shot.

In theory, a longer barrel offers more room for bullet expulsion. But if the amount of gunpowder to be burned is held constant, the length starts becoming a drawback. And since you can't stuff more gunpowder into your ammo, it's essential to ensure you do not go too extreme on the barrel length. On the flip side, having a shorter barrel allows for easier close-combat shooting, which would otherwise be a challenge if you had a nine-inch barrel.

For hunting expeditions or other long-range requirements, the .300 AAC Blackout has a maximum effective range of approximately 460 meters. However, this maximum effective length is determined by the barrel's length, and the 460-meter distance is achieved by a nine-inch barrel. The barrel also plays a role in the drop rate of the bullet. For instance, the nine-inch barrel has a 100-inch drop at 410 meters, while a 16-inch barrel has a drop of a 100 inches at 440 meters.

From What Distance Will a .300 Blackout Kill a Deer?

The .300 Blackout is quite effective when hunting for animals like wild pigs, deer, or varmint. However, for the best results, we suggest that you use recommended hunting ammunition variants of the .300 Blackout, like the 125-135 grain range. These rounds can work well in taking out deer at distances of up to 300 meters, depending on who is handling the rifle and the shooting conditions they're in.

In matters of velocity comparison, different barrel lengths for the .300 Blackout sit within the 25-50 feet per second per barrel velocity rule that governs most firearms. For example, with a 10.5-inch barrel, the .300 Blackout clocks an average velocity of 2200 feet per second. While on a 16-inch barrel, it reaches speeds of approximately 2400.

Having a longer barrel also provides more time and surface for the bullet to stabilize from the point of firing to the point where it exits the muzzle. This ensures that the bullet maintains a more accurate and precise trajectory upon exit and improves the target-inaccuracy issue. A longer barrel also offers a long line of sight for you to better aim your rifle even if the rifle is not equipped with sight extensions.

A big factor of consideration when picking a rifle, its barrel length, or ammunition is the type of target you wish to use it on. Though the .300 Blackout was designed to offer the best results in close-range targets, you can use it for long-range targets as well. For long-range targets, barrel lengths of up to 16 inches are available. Nothing further than that is as effective since the gunpowder burning would be inefficient in the spare room.

Is a 16-Inch Barrel Good for the .300 Blackout?

A 16-inch barrel is the longest available barrel for the .300 Blackout, and it is quite effective when it comes to long-range targets. Plus, the long barrel compensates for its rather laborious maneuverability.

The length of a barrel also dictates the rifle's twist rate and thus the bullet as it travels down the barrel. The twist rate is when the bullet twists within a barrel once fired, which helps keep it at a high velocity and helps maintain accuracy. A longer barrel has a slower twist rate and provides more power and accuracy, which is better for long-range targets. A longer barrel, because of its increased surface area, provides more room for cooling in instances where you shoot continuously.

Whether you decide to go long or short on your barrel is entirely a matter of what you are shooting at and where the shooting is taking place. If it's inside your house in home-defense scenarios, a short barrel will allow for better maneuverability. And if you are out in the wild shooting at some long-range game, a longer barrel will give you both the power and accuracy advantage. But all things considered, the .300 Blackout will surely deliver whenever it's put to the task.

How Do You Build an AR-15 in the .300 Blackout?

One important consideration before you set out to build your AR-15 in the .300 Blackout is knowing the scope of usage of your gun. Will the gun be a 'do it all' for long-range or short-range shots? When picking out a muzzle for your assembly, keep in mind the muzzle's compatibility with available suppressor fittings. Your muzzle choice should also be in consideration of the flash produced and the muzzle rise with every shot.

When picking an upper for the setup, you can go either with a T-Marked or a Non-T-Marked, depending on your personal preference. For a more economical build experience, getting a full lower build kit will save you some bucks. The build kit comes with well-documented manual instructions for putting together the firearm, along with well-labeled parts, which are all individually packaged.

Contact our team at 80 Percent Arms to learn more.