Posted by on 10/15/2021 to
The AR15 is a wonderful machine. It efficiently fires round after round, even automatically, smoothly, and with little recoil. Part of this elegant system is the Gas System. There are two different types of Gas Systems currently in use with the AR15, the Direct Impingement, and the Gas Piston. Which one is right for you and your AR? Like most things AR, there are advantages and disadvantages to each, so it is up to you to decide which is best. That said there is a favorite currently, but that doesn’t mean the favorite is the best one.
The gas systems of the AR are integral to it working correctly and efficiently. They do this by using the gas in the barrel that was created when the round was fired. This gas travels at a high velocity and provides the energy and force that cycles the spent shell out and the new round into the chamber. In both systems, the gas travels down the barrel until it hits the gas block. At that point, either the gas continues down the gas tube back towards the upper receiver or interacts with a piston that interacts with the upper receiver.
The most popular gas system by far right now is the Direct Impingement System. This may not be surprising as it has been around the longest, and is what the AR-15 originally came with, there was no other option. What this system does is allow the gas to travel from the gas block down a gas tube and through the upper receiver. Once it gets to the Upper Receiver the gas hits the gas key which is attached to the Bolt Carrier Group. This pushes the BCG back which engages the buffer system, a spring system that then pushes the BCG forward again picking up the next round in the process and positioning it in the chamber. As the BCG is getting pushed back the spent casing of the last round is ejected. Sounds like a great system right? It is; it’s very efficient. The drawback is that the gas, which was created by an explosion, is understandably dirty. This can cause fouling in the Upper Receiver, carbon that gets on everything and needs to be cleaned off. So the advantages to this are that it is very efficient, lightweight, and less money due to fewer parts. The disadvantage is that it is messier, requiring more frequent and thorough cleaning. It can also heat up the BCG which can cause problems for the lubricant used on it. Both of these disadvantages can reduce the lifespan of these parts as well as the reliability of the AR.
The other gas system is the Gas Piston System. This is different in that once the gas hits the gas block it pushes a piston which then pushes the BCG back and expels the spent casing. After the gas has pushed back the piston it is vented into the air just above the gas block. This makes for a cleaner upper receiver and clip and a cooler and cleaner BCG. Also, this system is adjustable so it can be fine-tuned much more than a Direct Impingement System. It is often the favored system for sound suppressed and pistol length builds, due to the way it deals with the gas. It is said to affect accuracy very slightly because the moving rod affects barrel harmonics. This is the kind of thing that while probably technically true, most people won’t notice, because most people are not that precise. There are claims that the technology has improved and as long as you are getting a new, quality system, there is no reason why these things need to affect you. This system also seems to cause more recoil, due to a weight in the form of the piston being pushed in your direction. Other disadvantages are that it’s anywhere between a couple of ounces to a pound heavier, it costs more, and of course, adds complexity which means more things to break. Even with all that, there are more and more people who are convinced that the Gas Piston System is the way to go. The new ones have seen improvements to the point where you may not be able to tell the difference. There are many people out there who have both but favor their Piston ARs.
Ultimately it is a personal choice and a point of preference as to which system is best for you. If you know someone who has a different system than yours, ask them if you can try it out. Or bite the bullet and get your own, it is a bit of an investment, but if you’re planning on a new build anyway, why not? An AR can be converted from the traditional Direct Impingement to the Piston System with just a change in BCG, gas block, and of course the system itself.