If you plan to build your .300 blackout AR-15 or replace parts on your existing firearm, you need to use well-made products. It is also essential to know how the action and gas system function.
The gas system is a critical part of the AR-15. It allows your firearm to cycle and function as a self-loading firearm. The length must be relative to your firearm’s barrel length because a gas system in the wrong size may cause jams or excessive wear.
Best .300 Blackout Gas Systems
1. Aero Precision Melonite Pistol Length Gas Tube
Aero Precision manufactures high-quality AR-15 and AR-10 parts such as lower and upper receivers, barrels, handguards, and bolt carrier groups.
This pistol-length gas tube is made entirely of stainless steel, featuring an overall length of 6.6875” and a weight of just 0.2 oz. The package also includes a gas tube roll pin, eliminating the need to purchase one separately.
This product features an anodized black Melonite finish, which not only completes the look of any black AR-15 but also increases its surface hardness, providing additional protection against wear and tear, corrosion, and heat.
Like all other Aero Precision products, this gas tube is 100% manufactured in the USA.
2. Guntec USA AR-15 Pistol Length Gas Tube
Guntec USA is an Arizona-based manufacturer of AR-15 parts established in 1989 and is renowned for their big-bore and pistol-caliber AR parts. The company also produces standard AR-15 and AR-10 parts.
Guntec AR-15, pistol-length gas tubes, measure 6.625” and are made from industry-standard 304 stainless steel. This gas tube is ideal as a spare or replacement part for all your short-barreled AR platforms.
These gas tubes are available in either silver or black Nitride finish, increasing fatigue strength and providing excellent protection against wear and corrosion.
3. CMC Triggers AR-15 Pistol Gas Tube
CMC Triggers is well known in the firearms industry for its drop-in trigger kits, but this Texas-based manufacturer offers a full line of spare AR-15 and AR-10 parts for all your building or replacement needs.
The CMC AR-15 pistol-length gas system is made using 304 stainless steel, coated in a black Nitride finish. Nitride is commonly used in many firearm parts to improve corrosion resistance and surface hardness, increasing durability and service life.
Like other CMC Triggers products, this AR-15 pistol-length gas tube is 100% manufactured in the USA at the company’s Texas production facility.
4. Spike’s Tactical Melonited Gas Tube Pistol Length
A pioneer in the world of AR-15s, Spike’s Tactical has long been considered one of the go-to manufacturers for high-quality AR-15 and AR-10 parts.
The Spike’s Tactical Melonited Gas Tube is one of the best values for the money if you’re looking for a durable yet affordable gas system for your AR-15. It features a highly durable Melonite finish, similar to the one used on Glock steel slides. The pistol-length model weighs just 0.38 oz.
A stainless steel roll pin is included in the package, allowing you to install it into your AR-15 gas block right out of the box. This part is ideal for builders looking to make the firearm of their dreams.
5. Noveske Gas Tube Pack Pistol Length
When it comes to high-quality AR-15 parts, Noveske is at the top of many shooters’ lists. Noveske AR-15 parts are some of the best-rated for competition and high-volume shooting.
Noveske gas tubes are made of high-quality stainless steel and are a perfect fit for their low-profile gas blocks, which allow builders to install longer handguards and the front sight of their choice.
This pistol-length gas tube comes in a special Gas Tube Pack that comes with a free gas tube roll pin and gas block dowel pin, reducing the number of parts you need to buy separately to complete your ideal AR build.
6. V Seven Extreme Environment Pistol Length Gas Tube
V Seven Weapon Systems is an innovative AR-platform rifle and spare parts manufacturer, focusing on robust and lightweight materials such as titanium and lithium-aluminum.
The V Seven Extreme Environment AR-15 Gas Tube is made from heat-treated Inconel, a nickel-chromium superalloy. This material possesses excellent resistance to high temperatures, corrosion, and oxidation, making it one of the most durable gas tubes available on the market.
For additional protection against wear and tear, this item features an Ionbond Diamond-Like Coating (DLC). The result is a gas tube that tolerates repeated magazine dumps, even in full-auto.
Although it is a little more expensive than most other gas tubes, if you need the most durable gas tube on the market, this is the one to get.
How Does The AR-15 Gas System Work?
The AR-15 is a gas-operated, self-loading firearm.
- Self-loading means that as long as there is ammunition in the magazine, the firearm will automatically chamber a fresh round after firing the previous shot, repeating with each trigger pull until the magazine runs dry or a malfunction occurs – this process is called cycling.
- Gas-operated is a family of firearm actions. A gas-operated firearm uses part of the hot propellant gases generated by a fired cartridge to cycle.
There are many types of gas-operated actions. Military rifles such as the M16 and M4 use the Stoner Direct Impingement action(named after the AR-15’s designer, Eugene Stoner), which employs a gas system composed of two parts: the gas block and the gas tube. As derivatives of the original M16, most civilian AR-15s use the same Stoner DI action.
The gas block function is simple: situated directly above a hole in the barrel (the gas port), it redirects the propellant gases into a gas tube. This tube runs parallel to the barrel and sends the gases directly into the AR-15’s upper receiver, pushing the bolt carrier group (the part which chambers and extracts cartridges) rearwards.
The terms “gas tube” and “gas system” are interchangeable, as there are multiple lengths of gas tubes.
The AR-15’s gas tube’s length is critical to the firearm’s proper operation because of a phenomenon called dwell time. This is the time during which a bullet is in the barrel after firing a shot. The longer the barrel, the longer the dwell time.
A critical moment of dwell time is when the bullet has passed the gas port but has not yet left the barrel. This is when the propellant gases enter the gas block and circulate into the gas tube. As soon as the bullet leaves the barrel, propellant gases stop flowing into the gas system.
The gas system needs to receive the right amount of gas to function reliably.
- If too much gas flows, the system is overgassed. It will function, but the gas system will be stressed more than is necessary, resulting in higher recoil and accelerated part wear.
- If there isn’t enough gas flow, the system is undergassed and risks sustaining malfunctions such as a failure to lock on an empty magazine, failure to extract, or eject failure.
Gas System Lengths
There are different gas system lengths available on the AR-15, but most shooters are likely only to encounter four: Pistol-length, Carbine-length, Mid-length, and Rifle-length.
- Rifle-length gas systems are the longest, measuring 12” from gas port to receiver. The rifle-length gas tube is the original design, exactly as introduced on the M16 rifle in 1959. Gas tubes of this length are suitable for barrels at least 18” long.
- Mid-length gas systems are a compromise between carbine-length (detailed below) and rifle-length systems. The gas block distance is 9” and best fit on civilian 16” barrels, although they function on barrels between 14” and 20”.
- Carbine-length gas systems are used by military carbines, such as the M4 and M4A1. They are 7” long and will function on barrels between 10” and 18”, with the best fit for 14.5” barrels.
- Pistol-length gas systems are the shortest type of AR-15 gas system available, intended mainly for short-barreled platforms, such as AR pistols and certain specialty subcarbines. With a port distance of just 4”, gas systems of this length are usually only suitable for barrels measuring 10” or less. However, there is one exception – the .300 Blackout AR-15s.
.300 Blackout generates less pressure than 5.56x45mm or .223 Remington, which reduces the risk of overgassing but increases the risk of undergassing.
Subsonic .300 BLK ammunition generates even less pressure than supersonic rounds, translating into fewer propellant gases generated with each round fired.
An AR-15 chambered in .300 Blackout must harness as much of these gases as possible to avoid undergassing the gas system and ensure reliable operation with subsonic ammunition.
Therefore, a pistol-length gas system is highly recommended, even on 16”-barreled rifles. You don’t need to worry about wearing your AR-15 out if you shoot supersonic ammunition, even through a pistol-length gas system, as the reduced pressure compared to standard 5.56mm ammunition will not stress the firearm as quickly.
AR-15 builders and gunsmiths consider gas tubes to be consumable items. Even if you purchase a highly durable model, the gas tube is likely to break in the event of a catastrophic failure.
If you are a competition shooter or simply enjoy shooting high volumes of ammunition at a time, such as mag-dumps, you are more likely to sustain a gas tube failure.
Most shooters recommend keeping at least one spare. Fortunately, AR-15 gas tubes are inexpensive. If you possess the armorers’ tools required to build your AR-15, installing or replacing the gas tube yourself is possible and relatively easy.