Understanding Gas Systems
What is a Gas System?
The AR-15 platform has become an icon of American firearms, renowned for its modularity, adaptability, and widespread appeal. From recreational shooting to professional applications, its versatility stems from the sheer number of configuration options available to owners. A critical element that significantly impacts an AR-15’s performance, reliability, and overall feel is the gas system. Choosing the correct gas system is paramount to achieving optimal functionality. This article delves into the intricacies of two popular gas system lengths, the Rifle Length Gas System (RLGS) and the Mid Length Gas System (MLGS), providing a comprehensive comparison to help you determine the ideal choice for your AR-15.
Gas System Lengths
Understanding the nuances of the gas system is crucial for any AR-15 owner. It’s more than just a component; it’s the engine that drives the entire cycle of operation. At its core, the gas system utilizes the expanding gases generated by the combustion of propellant in the barrel. As the bullet travels down the barrel, some of this high-pressure gas is siphoned off through a gas port drilled into the barrel. This gas travels through a tube, then enters the bolt carrier group where it drives the bolt carrier rearward, extracting the spent cartridge, ejecting it, compressing the buffer spring, and then under spring pressure returning forward, chambering a new round. The precise timing and amount of gas used are critical for proper function. Too much gas, and the rifle may experience excessive recoil, increased wear and tear, and potential malfunctions. Too little gas and the rifle might fail to cycle reliably.
Gas Port Sizing
Different gas system lengths exist to optimize performance based on barrel length and other factors. These lengths are generally categorized as Pistol, Carbine, Mid, and Rifle. The location of the gas port, along with the length of the gas tube, dictates the dwell time—the amount of time the bullet spends traveling down the barrel after the gas port and before the bullet exits the muzzle. Dwell time is directly correlated to pressure, as gas pressure gradually decreases the further the bullet travels down the bore. The size of the gas port is another important factor. Gas port sizing must be matched to the specific barrel length and the ammunition you intend to use. An undersized gas port can lead to short stroking and failure to cycle, while an oversized gas port can result in overgassing, causing malfunctions, and increasing wear on the components. Achieving the right balance involves careful consideration of all components involved.
Rifle Length Gas System (RLGS)
Description of RLGS
Let’s explore the Rifle Length Gas System (RLGS) in detail. This system typically features a gas tube that extends along the barrel for a longer distance, with the gas port located further down the barrel. The longer gas tube is characteristic of barrels that are traditionally twenty inches in length, though it can sometimes be found on shorter barrels as well, when designed to improve smoothness of operation.
Advantages of RLGS
One of the primary advantages of the Rifle Length Gas System is its smoother recoil impulse. Because of the increased distance the gas has to travel, and the longer dwell time, the rifle experiences a softer, more gradual push during firing. This is often perceived as less felt recoil by the shooter, allowing for quicker follow-up shots and greater comfort during extended shooting sessions. A rifle operating with a rifle length gas system gives time for the expanding gas to provide a steadier push on the bolt carrier group.
Another benefit of the RLGS is its potential for reduced wear and tear on internal components. The smoother cycling action, with the gas acting on the bolt carrier group over a longer period, puts less stress on parts like the bolt, bolt carrier, buffer, and springs. This can potentially extend the lifespan of these components and reduce the likelihood of malfunctions.
Furthermore, the Rifle Length Gas System often proves more reliable with a wider range of ammunition. The design is less sensitive to variations in gas pressure, meaning it’s less prone to overgassing, which can lead to malfunctions with certain ammunition types. The longer dwell time allows for a more consistent extraction and ejection cycle, even with lower-powered loads that might not reliably cycle a shorter gas system. The rifle length gas system helps create a more consistent operation.
Disadvantages of RLGS
However, the RLGS also has some drawbacks. One of the main disadvantages is that it may not cycle reliably with all types of ammunition. In some cases, particularly with extremely low-powered loads or certain types of subsonic ammunition, there might not be sufficient gas pressure to cycle the action fully.
Another consideration is the required handguard length. The longer gas tube necessitates a longer handguard, which can potentially affect the maneuverability of the rifle, especially in confined spaces. A longer handguard might feel less comfortable to some shooters or make the rifle more cumbersome to handle, particularly when moving around in an area where space is limited.
Additionally, the Rifle Length Gas System tends to be slightly heavier compared to shorter gas systems. This weight increase is due to the longer gas tube and potentially a longer handguard. While this difference might be negligible for some, it can contribute to overall fatigue during prolonged use.
Mid Length Gas System (MLGS)
Description of MLGS
Now, let’s turn our attention to the Mid Length Gas System (MLGS). This system is designed to find a balance between the efficiency of the carbine-length gas system and the smoother operation of the rifle-length gas system. The mid-length gas tube is located between the gas block and the front sight post on a 16″ – 18″ barrel. This setup is popular because it provides a good compromise between recoil management, reliability, and overall maneuverability.
Advantages of MLGS
The primary benefit of the Mid Length Gas System is the improved recoil impulse compared to a Carbine Length Gas System. The gas port is positioned further down the barrel, which means the gas pressure is slightly lower than that of a Carbine Length Gas System at the time of gas system activation. This contributes to a smoother recoil cycle and can lead to faster follow-up shots. It is also much better than the Carbine Length gas system, and it is often considered the sweet spot between the two extremes.
Furthermore, the Mid Length Gas System aims to offer a balance between recoil management, reliability, and maneuverability. It’s designed to provide a more comfortable shooting experience while maintaining consistent cycling performance. This makes it well-suited for a wide range of shooting applications. The MLGS, therefore, provides a much more balanced approach to the use of a firearm.
The Mid Length Gas System generally provides a good balance between barrel length and handguard length. Many shooters find that a 16-inch or 18-inch barrel with a mid-length gas system strikes an ideal balance between compactness and ballistic performance. This provides for easier maneuverability than a full-length rifle, with better performance and more consistent cycling.
The Mid Length Gas System often proves to be a very reliable choice, with far less wear and tear compared to carbine-length gas systems. This enhanced reliability is attributed to the reduced gas pressure, and the smoother cycling action. This balance between reliability and durability is a primary factor for its widespread acceptance and popularity.
Disadvantages of MLGS
However, the Mid Length Gas System also has some drawbacks. The recoil impulse might still be slightly sharper compared to the Rifle Length Gas System. While the MLGS offers smoother recoil than a carbine-length system, it generally doesn’t feel quite as gentle as a RLGS.
Additionally, the Mid Length Gas System is sometimes susceptible to overgassing with specific loads, and may also cause malfunctions. The exact gas port size and ammunition compatibility should always be thoroughly tested. These adjustments can include the use of adjustable gas blocks to fine-tune the system and reduce the risk of overgassing.
Head-to-Head Comparison: RLGS vs. MLGS
Recoil Impulse
When comparing Rifle Length Gas System and Mid Length Gas System, several factors deserve careful consideration. The recoil impulse differs noticeably between these two systems. The RLGS, with its longer dwell time, generally provides the softest recoil experience. The MLGS, although improved over the carbine length gas system, is somewhat sharper than the RLGS.
Cycling Reliability
Cycling reliability can also differ. The RLGS, with its slower and more consistent gas pressure, often exhibits higher reliability across a broader range of ammunition. While the MLGS is generally reliable, it might require more careful attention to gas port sizing and ammunition compatibility. Both systems are designed to be reliable, but the rifle length gas system is often chosen for its superior reliability.
Wear and Tear
Wear and tear on internal components is another important point. The smoother cycling action of the RLGS, with a more gradual and extended gas impulse, tends to reduce the stress on the bolt, bolt carrier, buffer, and springs, potentially extending their lifespan.
Barrel Length Considerations
Barrel length is closely related to the optimal gas system. Generally, RLGS is most common on twenty-inch barrels, while the MLGS is often used on sixteen to eighteen-inch barrels. The relationship between barrel length and gas system plays a significant role in the overall performance of your AR-15.
Maneuverability
Maneuverability is another key consideration. Because the Rifle Length Gas System requires a longer handguard, it’s often less maneuverable in close quarters. The shorter handguard associated with the MLGS contributes to increased maneuverability.
Cost
Cost plays a role in the overall setup of the platform. Generally, the cost difference between RLGS and MLGS components isn’t significant. However, the overall cost will change based on the other components of your setup.
Choosing the Right System
Factors to Consider
Choosing the right system involves carefully assessing your needs and preferences. Consider the intended use of your AR-15. For long-range shooting or applications where the softest recoil is paramount, the RLGS is often preferred. For general-purpose rifles, home defense, or scenarios where maneuverability is a priority, the MLGS is often an excellent compromise. Barrel length is a significant factor. If you prefer a longer barrel, the RLGS might be the better choice. If you prefer a more compact rifle, the MLGS, especially on a 16-inch or 18-inch barrel, offers a good balance. Ammunition selection should also influence your decision. If you plan to use a wide variety of ammunition, including some low-powered or subsonic loads, the RLGS might offer greater reliability. Personal preferences are critical. Some shooters are more sensitive to recoil than others. If recoil is a significant concern, the RLGS might be the best choice.
Recommendations Based on Scenario
For long-range shooting, the RLGS often delivers the smoothest shooting experience and the highest level of reliability. Its reduced recoil allows for faster target reacquisition, and its consistent cycling enhances accuracy and confidence. The rifle length gas system is especially useful when it comes to the use of a scope. For general-purpose rifles or home defense setups, the MLGS frequently provides a great balance of performance, recoil management, and maneuverability. The MLGS is a great choice when considering its versatility.
Other Considerations
Adjustable Gas Blocks
There are several additional factors that may impact your system’s performance. Adjustable gas blocks offer a higher degree of customization. These gas blocks allow you to fine-tune the gas flow to match your specific ammunition, barrel length, and operating conditions. They’re particularly useful for mitigating overgassing or for running suppressed.
Gas Port Sizing Importance
Gas port sizing is another crucial consideration. The gas port must be sized correctly for your barrel length and ammunition. An incorrect gas port size will lead to malfunctions.
Buffer and Spring Role
The buffer and spring also contribute to the AR-15’s cycling process. These parts work in tandem to absorb recoil and return the bolt carrier to the battery. A properly matched buffer and spring are essential for reliability and smooth operation.
Conclusion
In conclusion, both the Rifle Length Gas System and the Mid Length Gas System offer unique advantages. The RLGS provides the softest recoil and enhanced reliability, particularly with a wider range of ammunition. The MLGS strikes a good balance between recoil management, reliability, and maneuverability, making it an excellent choice for many applications. Choosing the right gas system requires a careful evaluation of your intended use, barrel length preferences, ammunition selection, and personal preferences. Consider which system best suits your needs and your shooting style. Ultimately, the “best” gas system is the one that delivers the best performance and reliability for your specific AR-15 configuration. Take the time to research and select the components that align with your individual goals and shooting style. By understanding the nuances of both the RLGS and the MLGS, you can make an informed decision and build an AR-15 that meets your specific requirements.
