If you are an AR-15 weapon owner, then gas blocks are something worth taking note of.
Why? Because installing an adjustable gas block on your AR-15 will work to reduce the wear on your weapon’s working parts. It also helps reduce felt recoil and, in turn, should improve reliability of use and improve accuracy. These factors alone should tell you that the investment required to purchase an adjustable gas block should be seen as a worthy functioning accessory.
In this review, we will take a look at important ‘gas block’ related issues. We will also review products from four of the best adjustable gas blocks manufacturers currently available.
Armed with this information, it should help you make an informed decision on which adjustable gas block is fit for your shooting purpose. But before all that, we’ll start with…
Giving a brief explanation of what a gas block is should tell us what function it fulfills.
Location, Location, Location…
Here we are talking about the general placement of a typical factory gas block. It is part of the front sight assembly, is placed (pinned) on the barrel, and sits to the front of the weapon’s handguard.
Rifles featuring free-float handguards made from aluminum usually have a low-profile gas block that is placed under the handguard.
What function does it perform?
The purpose of a gas block is to take a portion of the hot gas from a fired bullet. This comes through the barrel’s gas port. It works by directing gas into the gas tube. It is the gas tube that drives the weapons bolt carrier and cycles the action.
Factory gas blocks are mostly of the ‘fixed’ type…
Shooters who purchase complete, factory-made AR-15s will find that in most cases, the gas block is fixed. Being fixed means, these gas blocks only perform by providing a path for the gas from barrel to gas tube.
A weapon with a fixed gas block will use all of the gas and pressure coming from the gas port in the barrel to cycle the action. But, the majority of rifles built on the AR-platform intentionally have more gas than is needed. The reason for this is that if the gun gets dirty, this additional gas will help it to continue cycling.
Unnecessary recoil and wear on parts…
As just mentioned, AR-type weapons with fixed gas blocks are often overgassed. The two major issues related to this are heavier recoil and continually increased wear on weapon parts.
That’s the advantage of having an adjustable gas block. As the name suggests, these gas blocks allow for a portion of the gas flow to be cut off. This means the action is driven less forcefully and, in turn, reduces felt recoil and wear on your weapons parts.
As can be seen, a fixed gas block is a ‘one size fits all’ design approach for rifles. It does not take into account a whole host of shooter profiles such as:
Adjustability means getting more from your weapon. And installing an adjustable gas block gives you the ability to fine tune your weapon. This means you are achieving more from your chosen rifle build. In essence, it allows the parts of your weapon to work together in a more efficient manner.
Reasons for fine tuning…
Fine tuning the gas required to run your rifle system can be achieved in a variety of ways. Three examples being:
Reducing recoil
With a fixed gas bolt, there is more gas flowing to the rear of your rifle. And more force equals more felt recoil. As we all know, the heavier the recoil, the harder it is to control your rifle. This can affect your shot accuracy. Using one of the best high quality adjustable gas blocks on the market will allow you to reduce the gas flow, reduce the felt recoil, and in turn, help with shot accuracy.
Overgassing runs your rifle hotter and dirtier
If your rifle is producing excess gas, then its internal temperature is increased, and it will run hotter. The hotter it runs, the more carbon build-up you will get, which can lead to weapon functioning issues such as failure to feed or failure to fire.
You can still ‘overgas’ when the situation demands
It needs to be pointed out that there are situations where it is wise to overgas your rifle. Two good examples here are if you are having a particularly hard, active session with your gun and intend to continue. And secondly, if you are shooting (and intend to continue) in conditions that are particularly dirty.
There is certainly no reason to spoil a good thing! In this respect, an adjustable gas block is up to the job. You simply open up the gas block and use it with increased gas flow.
Ease of Adjustment
Shooters will find that the best adjustable gas blocks are designed with ease of adjustment in mind.
The common way to achieve this is through the use of a simple key that gives access to the adjustment points. This is regardless of whether your rifle has a rail system over the gas block or not.
As with all weapon accessories, you will find different types of adjustable gas blocks available. Here’s a brief overview of what you can expect to find. When referring to adjustable gas blocks, you will commonly hear the terms: “Cut-off” type and “Bleed off” type.
Bleed off design
This type of gas block incorporates an adjustable system with numerous positions to regulate the gas flow. It does so by “bleeding” the gas out front and away from the shooter.
Using an adjustable gas block with a bleed off design offers greater flexibility of gas flow levels.
Cut off design
These adjustable gas blocks do what they say on the tin! A cut off designed gas block literally has an “OFF” setting positioned on the block itself. In fact, it has three settings: Unsuppressed, Suppressed, and Off.
This design is favored by shooters who mostly use their weapons suppressed and need a way to completely shut off the gas system. Suppression shooters will also find ‘Closure’ type gas blocks available.
Low profile versions
While standard size adjustable gas blocks certainly work, some shooters prefer a low profile version. This simply means that a low profile adjustable gas block has been precision machined with the intention of taking up the least amount of barrel space on your gun.
Gas block sizing
The AR-15 platform offers different designs and barrel diameters. Therefore, gas blocks come in different sizes in order to fit these barrel gas journals.
Two popular examples:
A special mention goes out to bull size barrels!
While not as popular, some AR-15 shooters use “Bull Barrels”. As the name suggests, these are mostly heavier and larger than the more common barrels we’ve mentioned. In this case, the inner diameter for most gas blocks to fit these larger sized barrels are either 0.875-inches or 0.936-inches.
We will shortly feature a buying guide, which should help pinpoint considerations for an adjustable gas block that best suits your shooting style. But first, let’s review some of the very best designed adjustable gas blocks currently available 2024 for purchase…
J P Enterprises are undoubtedly among the pioneers of the adjustable gas block concept.
A variety of adjustable block formats…
As such, they produce these accessories in a variety of formats. This includes adjustable gas blocks with:
Smoother cycling is yours
You can easily replace a factory front sight gas block with one from the J P Enterprises range of adjustable gas blocks. By doing so, it gives the ability to tune your gas system in order to achieve smoother cycling and operation. This is of great advantage to those shooters who use both factory and custom-loaded ammo for match shooting and in varmint rifles.
Secure fixing and ease of use
A set of hex head set screws allow you to clamp the block to the barrel in a secure fashion. Full installation instructions are included with purchase, and most AR-15 shooters will find this straightforward. However, those who prefer to have the installation carried out by a gunsmith will find this a fast, cheap task for them to complete.
Once installed, you use a simple set screw to control the flow of gas. This means you can easily customize settings for each load used.
A popular example
As mentioned, J P Enterprise offers a wide variety of adjustable gas blocks. One of their most popular is the .750 Adjustable Gas Block. Shooters in all disciplines, from competitions to hunting (as well as law enforcement!), have taken to this version.
It is made from good quality 416 stainless steel and holds securely in place using four screws. You can also choose between 2-types of hardened finish. As for ‘fit’, this low-profile design seats snugly under a good number of AR-15 handguards.
