Most of us - at least in the early stages of our relationship with the AR-15, go through the same upgrade process. The first thing is to mount an new sight or red dot. Next, we upgrade it with a buttstock that would ideally suit us.
After some time has lapsed, we start to look for a better trigger and customized upper receiver. Usually near the bottom of the list, too often overlooked, is the gas block. The gas block, paired with the gas tube, is a part of a system that is the most underappreciated contributor to a gun's performance and reliability.
In this article, we will talk about the purpose and use of a gas block, as well as provide you with some of the best options on the market.
Comparison of the Best AR-15 Gas Blocks
| PRODUCT | DETAILS | ||
|---|---|---|---|
 Our Top Pick | SGB Geissele Super Gas Block |
| View Latest Price |
 | ODIN Works Inc. AR-15 Low Profile Gas Block |
| View Latest Price |
 | VLTOR Weapon Systems - AR-15 Gas Block Low Profile |
| View Latest Price |
 | Superlative Arms LLC - AR-15 Adjustable Gas Block .750" Clamp On |
| View Latest Price |
The Purpose of the Gas Block
The gas block is the component that straddles the barrel and fits over the gas port. It manages the flow of hot gas through the gas hole down to the gas tube and further on to the head of the bolt carrier.
The AR-15 has been operating just fine for over 50 years, utilizing a direct impingement gas operating system. While the AR platform has been constantly modified and improved over time, the typical factory version has stayed pinned onto the barrel.
Known as a fixed front sight gas block, these simple and robust devices transfer a fixed amount of hot gas through the tube back into to the bolt carrier group to cycle the action. In most AR-type rifles, the fixed models provide more gas than is needed. This causes more recoil and increased wear on parts. And that means an over-gassed rifle runs hotter and dirtier.
What is an Adjustable Gas Block?
The industry soon realized that this simple, but critical component could be improved by adding a small metering screw on the side of the gas block. Furthermore, the best contemporary adjustable ones on AR-15s are modernized with spring-loaded detents that lock the set gas flow in place. Audible clicks help in identifying the setting.
The concept of an adjustable-gas system can be vividly explained as a valve that regulates how much hot gas is directed back into the upper receiver. Unlike the standard philosophy that one-size-fits-all, the adjustable gas block is designed to allow reliable use of different kinds of ammunition. It also allows for suppressor use or upgrading of your rifle by helping adjust the weight.
An AR-15 with an adjustable gas block will decrease felt recoil, resulting in a faster follow-up shot. It will put less stress on the operating parts and due to the lower carbon build-up, your rifle will run cleaner and cooler.
Ultimately, when you add gas-tuning devices, your system will operate more smoothly and muzzle rise will be reduced. That means you also get a more accurate shot.
As a critical link in the chain, this component needs to be constructed from quality and durable materials like carbon steel, stainless steel, or even titanium. All of them have their benefits and risks. Carbon steel is prone to rust and stainless steel is harder to machine. Titanium is approximately 40% lighter than steel, making it an excellent option for AR-15 gas blocks. But it is much more expensive and difficult to machine than the other options.
How to Choose an AR-15 Gas Block
Finding an AR-15 gas block will take some time and sharp observation skills. Thatโs because you need to know some of the features and characteristics that make a gas block great compared to those that are considered bad in reliability and quality. Here are some things to look out for:
Price
The price tag might be of importance to you if youโre looking for a gas block on a budget. The important rule to follow is to always find the best quality and performance you can afford. You donโt want to waste money on a gas block that will turn out to be a disappointment. Also, donโt be afraid to spend a little higher in your budget range. The overall value of the gas block should matter more than the price itself.
Know Your Gas System
One thing to note is that an AR-15 can have a different gas system from one rifle to the next. So it would make sense to find a gas block that fits a mid-length gas system if your rifle has one. Pay attention to which gas system you have so you know which one will be the better choice for you.
Installation
Most of the gas blocks for an AR-15 will be easy to install. This means you wonโt have to enlist the services of a professional gunsmith and spend more money in the process. All you need are the right kind of tools and some minutes of your time to successfully pull off any gas block installation.
Quick Take - The Best AR-15 Gas Blocks
These are our recommendations for the best gas blocks for the AR-15:
Review of the Best AR-15 Gas Blocks
The following are the four best AR-15 gas blocks currently popular on the market. As you go through each one on the list, you should make a note of the characteristics and features. This way, you can find one that fits your ideal gas block. If you find one that matches your description, thatโs when you know you have a winner on your hands.
In this guide, weโll suggest the best AR-15 gas blocks in several formats, including small, low-profile units with lock screws that disappear under a rail system, ones with rails on top of the gas block, and one that clamps onto the barrel. Letโs begin by taking a look at the first AR-15 gas block on our list:
Best Overall:
SGB Geissele Super Gas Block
Pros
Cons
What Recent Buyers Report
New buyers were satisfied with the gas block. They were able to install it easily (assuming they had the right gunsmithing skills). Once installed, they were able to experience smooth shooting and cycling without any reliability issues.
Why it Stands Out to Us
The gas block is low-profile. But itโs slightly larger than some of the other low-profile gas blocks on the market. But make no mistake, it can still make the gas system stand out without sticking out like a sore thumb. Itโs measured at .750 inches in diameter and will likely fit most AR-15 rifles. But donโt assume that it is a universal gas block.
When discussing triggers, most of us have heard about the quality of Geissele products. Bill Geisseleโs company also offers this great, non-adjustable and low-profile gas block made of 17-4 stainless steel. The Geissele Super Gas Block (SGB) is the lightweight, low-profile model intended to tightly fit around a .750-inch diameter barrel found on most AR-15 and M4 Carbine firearms.
The SGB has two possible mounting solutions, a standard one for the casual target shooter and a bomb-proof installation. The latter is designed for duty weapons and combat situations and adds a completely new level of security. While everyone can do the first type of fastening, the bomb-proof installation requires at least an advanced hobbyist with a drill press, if not an experienced gunsmith.
On the negative side, weโve found some issues with a tight fit on stainless barrels. Also, this block doesn't fit all rail systems since Geissele`s profile is slightly larger than other low-profile gas blocks.
Who Will Use This Most
If you have a standard barrel AR-15 rifle, thereโs a good chance this gas block will fit very well. Since itโs made from high-quality steel, you also have the potential of keeping this on your rifle for years or even decades to come. So if you want something sturdy, great for most rifles, and will give you the best, most reliable shooting yet, this might be your kind of gas block.
Bottom Line
The SGB Geissele Super Gas Block might not be a universal gas block. But it can fit most rifles, thus making it widely available to average AR-15 rifles. If you want a gas block that is solid and will get the job done each time you fire your rifle, it starts with the right kind of accessory like this.
Runner-up:
ODIN Works Inc. AR-15 Low-Profile Gas Block
Pros
Cons
What Recent Buyers Report
As expected, new buyers were quite satisfied with the gas block. They were able to install this within ten minutes with the right kind of tools. Once installed, the gas block worked quite well with their preferred gas systems. One user said he was able to fire off 200 rounds without any reliability issues.
Why it Stands Out to Us
These gas blocks are available in different measurements. So there is always one that will be available to fit not just any gas system of an AR-15, but certain barrel sizes, as well. All of the gas blocks are made from high-quality steel but are finished with a nitride-based finish that adds on more durability. The likelihood of this lasting you a long time without any kind of damage or scuffing is pretty good. So if durability is your thing, this gas block could be what youโre looking for.
The ODIN Works Adjustable Gas Block is manufactured from carbon steel and super-alloys - called Inconel - which is resistant to high-pressure and heat. It was born out of their experience in the aerospace industry.
This version utilizes a front-facing Inconel adjustment screw and spring to ensure the proper functioning of the gas system. Featuring 20 adjustment points, the ODIN Works Rifle Gas Block can be tuned for silencer usage or weak/hot loads.
The ODIN Works Gas Block fits .750โณ diameter barrels and can be installed as easily as any other low-profile type. It is secured to the barrel with two set screws on the lower side. However, if you do not want to dimple the barrel, there is also a clamp-on version available.
Although this low-profile design fits most rail systems and handguards, there are some issues with the fit if youโre using a smaller diameter handguard.
Who Will Use This Most
This gas block will be used by most shooters depending on the size they choose. Most importantly, this will be a gas block for use by AR-15 users who want nothing more than smooth, reliable cycling and shooting. Donโt be shocked if youโre going through hundreds or thousands of rounds only to see no jamming or any other reliability issues.
Bottom Line
Odin Works Inc. AR-15 Low-Profile Gas Block will probably be what youโll need for your rifle if you need a gas block that will fit your rifle. Choose the size that will fit your rifle best and install it in minutes. Once youโre good to go, the shooting ability will be boosted quite a bit.
Best for the Money:
VLTOR Weapon Systems - AR-15 Gas Block Low-Profile
Pros
Cons
What Recent Buyers Report
This gas block was a hit with new users. Right off the bat, they noticed the extra durability that the black nitride finish provided. After testing it out by banging it on a hard surface, they were impressed with how there were no scratches. One user said he added the gas block in a few minutes and made his shooting ability a lot smoother.
Why it Stands Out to Us
This gas block is at the right size to fit most rail systems. So it will fit most AR-15 rifles without any fitting or alterations needed. It is a gas block that is so durable, you can throw it around, run it over with a car, or try and damage it any way you can. Itโs a tough unit that is small in size but impervious to all kinds of beatings.
The VLTOR non-adjustable gas block is a slim replacement for the cumbersome and classic fixed-sight tower models. It presents a carefully-assembled gas management system.
The popular VLTOR low-profile models are tiny and compact, keeping weight down. Theyโre an ideal choice for the ultralight build or when using a handguard that is mounted over the whole gas system.
Besides fitting the .750โ diameter of standard barrels, this is also made to fit lightweight barrels that feature a .625" diameter, commonly referred to as pencil barrels.
These are machined from 17-4PH stainless steel and 4140 carbon steel. They come in stainless steel or matte black phosphate finishes.
The VLTOR Low-Profile Gas Block is available in two different methods of attachment. You can elect for the more conventional screw-on option with set screws at the bottom or a clamp-on model that squeezes around the barrel.
Note that clamp-on models will not fit under an exposed bottom rail channel on the inside of the handguard.
Thereโs also one aesthetic negative. Because it covers only one-inch of the barrel's surface, after removing a regular front sight post, you will have silver taper pin hole showing where the front sight post was.
Who Will Use This Most
This will likely be used by AR-15 users that might be looking for an affordable gas block that is high in quality and easy to install, this is it. You shouldnโt discount this as some kind of cheap or flimsy kind of gas block. If you want reliable shooting without your bank account getting drained in the process, this gas block will be a perfect choice.
Bottom Line
The VLTOR Low Profile Gas Block with Screw Mount is the kind of gas block youโll want for your rifle if you want something tough and affordable. Plus, youโll be able to install this in a matter of minutes and instantly see the change in cycling. If you love your gas system, get a gas block that will work perfectly with it. This one, in particular, might be just that.
American manufacturer JP Enterprises targets the competitive shooter market. AR components from JP indeed offer competition-quality adjustable gas blocks.
JP Enterprises produces theirs from lightweight 6061 T6 aluminum or rugged 416 stainless steel for additional muzzle weight. They are intended to mount underneath many handguards on the market. Along with a standard clamp-on design, there is a two-piece model that allows for easier installation on barrels with pin-and-weld muzzle devices.
The JP clamp-style model is attached with four hex-head set screws instead of the usual two. Still, to clamp the block securely to the barrel, you need to add some Loctite on each screw.
The JP Adjustable Gas System offers easy access to the side gas adjustment and internally retained detent components. That means you will have no more lost parts.
Since JP gas blocks are much bigger than other low-profile blocks, they require you to choose a shorter handguard. But youโll still be able to attach accessories to the rails. Just be careful of the dimensions, because the gas adjustment screw, when backed out, interferes with some handguards.
Pros
Cons
What Recent Buyers Report
Recent buyers were able to easily install this gas block in a matter of a few minutes thanks to the clamp-on design. They were able to keep it securely on their rifles for a long time. One user said by the time this was installed, it was ready for a test drive at the range. After going through ten different 25-round magazines, the cycling was smooth and reliable.
Why it Stands Out to Us
This gas block does a good job of reducing pressure and preventing gas from bleeding out of the rifle. This prevents reliability issues from happening and makes shooting a lot easier. Plus, it prevents misfires from happening. So if you had issues with gas blocks in the past, this one will correct the common issues much better than most.
It was the only a matter of time until someone merged several gas-system functions into one. The Superlative Arms did it with its 3-in-1 Gas Block.
This SA device has united three different types, providing you with the performance of a standard non-adjustable, a restrictive adjustable gas block, and their newly- patented bleed off gas block.
Unlike other adjustable gun blocks, this model, in "Bleed Off" mode, will bleed the excess gas out from the front of the gas block. When using the bleed-off setting, you can tune your rifle to the peculiarities of the ammo and the rifle. Above all, you also get a perfect component if you are running a suppressor or using a pencil barrel.
This innovative design allows the rifle to shoot more softly and cleanly because the adjustment detent is placed outside of the block and, therefore, there is no contamination.
This gas block is a bit tall and limits your options for handguards. At the same time, the bleed-off might work better with a longer gas system instead of the high pressures with pistol length. While being a great system, some adaptations in this area would be helpful.
Who Will Use This Most
Expect this to be a gas block that can be easily installed by anyone. Since itโs a clamp-on design, it wonโt take you a long time. On top of that, youโll notice some changes in cycling ability almost immediately. So, if you want better cycling for your AR-15, this gas block will probably get the job done at almost a snap of a finger.
Bottom Line
The Superlative Arms Adjustable Gas Block Bleed Off might be what youโll need for your rifle to ensure that gas leaks occur and reliability issues will be kept to a minimum (or none at all). Either way, this is a good gas block to have on-hand if you want something easy to install to make life easier for you, the AR-15 user.
How to Install Your New Gas Block
For people familiar with AR builds, installing this upgrade is a relatively easy and straightforward operation that requires only the usual household tools.
- Remove flash hider from your barrel muzzle and forward handguard.
- Using a hammer and punch, unpin the factory gas block and remove it from the barrel.
- Install your new gas block using set screws or clamping screws to lock it into place. If you are dealing with an adjustable gas block, you might need to adjust the new gas block before reinstalling the handguard. Some of them have the locking screw in a location that makes it almost impossible to access with a handguard installed
- Reinstall your handguard and muzzle device.
If you are unfamiliar with tools and basic-level gunsmithing, you can easily find a reputable gunsmith to do this inexpensive gunsmithing job for you.
Considerations For Your Gas Block
As you might suppose, manufacturers offer these in appropriate sizes for your barrel. Most adjustable gas blocks are designed to be used with a typical medium-profile barrel with a diameter of .750โณ. However, there are also gas blocks for .936 diameter heavy bull barrels. The .625 diameter is another common size for pencil-profile barrels.
To ensure your AR runs reliably, you also have to purchase a gas tube of the correct length. Of course, you can always just keep your old one, too.
Besides the size, you should be aware of the different methods for attaching a gas block to the barrel. One type clamps on, but the most common mounting type is by slipping the block down the barrel and fixing it in place by set screws on the underside.
If you are plan on installing a free-float handguard to enhance the overall mechanical accuracy of your black rifle, then a low-profile gas block is a must. These are compact and disappear underneath long free-float handguards and its rail system. As you can imagine, they let you mount a longer rail system and allow more space for accessories.
Some gas blocks feature a Picatinny rail installed on top of them, making a perfect platform to mount a set of detachable, flip-up iron sights.
Conclusion
Aftermarket low-profile gas blocks make a huge difference in shooting comfort. They enable you to shoot faster and at the same time, reduce fatigue on your firearm. They also prolong the time between cleanings and cause heat reduction at the bolt.
That makes them one of the best upgrades you can make, especially if you plan to use a specific type of ammunition, handloaded ammo, or simply you want to mount any kind of suppressor.
Although adjustable gas blocks require more time for tuning, we strongly encourage this upgrade as the most significant performance improvement anyone can make to his or her AR-format rifle.
More reading: AR-15 Gas Piston Buyers Guide
