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Best Adjustable Gas Blocks [Complete Guide]

What if I told you one part could reduce your AR-15 rifle’s recoil, reduce wear, and even open up a wide variety of customization options?

Upgraded AR-15s
Upgraded AR-15s

Sound too good to be true?

It’s not, I promise.

Through an adjustable gas block, all this is possible.

An adjustable gas block offers a variety of advantages over a standard block.  Today we are going to go over those advantages, how to choose an adjustable gas block, and how to tune one.

Table of Contents


Why Bother with an Adjustable Gas Block?

It’s important to understand how direct impingement works to understand the value of an adjustable gas block.

Direct impingement works by taking advantage of the gasses produced by burning gunpowder to cycle the rifle.  The gas propels the projectile downrange and as it travels through the barrel a bit of that gas is bled off.

Direct Impingement
Direct Impingement

The gas goes through a port on the barrel, into the gas block (the bit we’re talking about today), and down the gas tube.

Superlative Arms Gas Bleedoff
Superlative Arms Gas Bleedoff

The gas goes back into the receiver, pushes the bolt rearward, which extracts and ejects the round.  It strikes the buffer which compresses a spring and sends the entire system forward after the spring hits its apex.

This entire system of operation relies on gas, and therefore the gas system becomes incredibly important.

The gas system is composed of the gas block and gas tube.  There isn’t much you can do with a gas tube, it’s a steel tube and the way it affects the rifle is generally tied to its length.

AR-15 Gas System Lengths
AR-15 Gas System Lengths

The gas block, however, is what bleeds the gas from the round to the gas tube.  The gas block can be adjusted or swapped out entirely to create a variety of changes in the rifle.

A fixed gas block allows a set amount of gas to flow through the system.  This is basically a one size fits all approach for rifles.

It doesn’t take into effect different types of ammunition, suppressor use, buffer weight, or BCG weight (and how many BCGs have vastly different weights).  

On the other hand, an adjustable block can be tuned to help you get the most out of your rifle build and to get all your parts working together a little more efficiently.

Tune Your Gas Block

An adjustable gas block is designed to allow you to fine tune the gas needed to run the system.

This allows shooters to tune their rifle for different ammunition types, for different weight internals, and of course suppressor use.

ar15 with suppressor
You can get much better results from your suppressor if you run it with an adjustable gas block.

Most rifles are actually over-gassed, meaning more gas flows through the system than necessary.  

Is this a bad thing?

I mean it’s not the kind of gas you pay by the gallon for right?  Well, there are a few issues with over-gassed rifles.

First, you are actually getting more recoil.  More gas flowing rearwards means more force, and more force means more felt recoil. 

This can even be true if you’re rocking the very best lightweight bolt carrier group.

Recoil makes for a harder to control gun, which degrades your accuracy.

An over-gassed gun is also going to run hotter and dirtier.  And not the fun kind of hotter and dirtier, either.

mind out of the gutter napoleon dynamite
Shame on you. Yes, you.

The extra gas and debris are going to raise the internal temperature and create a much dirtier gun.  

That extra carbon build up makes the rifle less reliable and increases the likelihood you’ll get a failure-to-fire or failure-to-feed issue. 

ar-15 double feed
Or the always exciting double feed, aka “Two Bullets, One Chamber” error.

Next, we should focus on wear. Over-gassing has also been tied to locking lugs wearing out well before their time is up.

The fact the bolt is being shot backward with excess force could result in a loosened gas key over time as well.

When to Crank Up the Gas

To be completely fair there is a time for over-gassing.  When a rifle has been run hard, is filthy dirty, full of carbon and sand, and moon dust – then you need that extra gas.

That extra gas keeps everything moving when the inside of your gun looks like a dirty litter box.  With an adjustable gas block when things get wicked, simply open the gas block up and let it flow.

palpatine let the gas flow
There are a time and place for everything, even listening to Palpatine. Dirty gun = crank up the gas.

Most adjustable gas blocks are designed to be used with a simple key to adjust the system.  These adjustment areas are easy to access, even with a rail system over the gas block.

Recapping the Benefits of an Adjustable Gas Block

An Adjustable Gas Block solves the following problems

  • Overgassing your rifle.
  • Reduces recoil.
  • Reduces wear and tear.
  • Makes your rifle run cleaner and cooler.
  • Let’s your rifle run more reliably when full of carbon fouling, sand, moon dust and the blood of your enemies  other debris.

How to Choose an Adjustable Gas Block

You choose an adjustable gas block the same way you choose most parts for your rifle.  You choose based on both your preferences and needs (and price, most of the time).

clamp on adjustable gas blocks
Editor’s Note: If you’re like me and have to be the prettiest peacock at the range, color may be important too.

 There are actually a wide variety of different options when it comes to adjustable gas blocks.


Like regular gas blocks, adjustable gas blocks come in a variety of different sizes.  You have the standard .750 for your normal medium profile barrel, and .875 for those special snowflake barrels.

We also have .936 for heavy bull barrels, and .625 for pencil barrels.

AR-15 Barrel Profiles
AR-15 Barrel Profiles

You’ll need to know the barrel profile you want, or you have, before choosing an adjustable gas block.  One note is that an adjustable gas block allows you make a very lightweight rifle, and a pencil barrel is beneficial to this.

Types of Adjustable Gas Blocks

Personally, I really like a fixed front sight.  Something about the stability and simplicity really appeals to me.

As a Marine, I’m quite used to the A-frame style fixed front sight and I like it.  This, unfortunately, means I really can’t use a free floating rail system.

My choices for full-length rail systems are also limited depending on where my front sight is fixed on the barrel.

BCM with Magpul 40-Rounder
BCM Recce 16

A free floating rail system can help with the overall mechanical accuracy of a rifle, and to run a free floating rail system I am going to need to run a low profile gas block.

A low pro gas block disappears underneath a rail system.  These low profile gas blocks allow the user to utilize a longer rail system that could extend all the way up to the muzzle device.

These rails are popular with those using the C-Clamp style of shooting like you’ll see in most competitive shooting matches.

LWRC, Ejecting Brass

There are also railed gas blocks.  These gas blocks are basically low profile gas blocks with a Picatinny rail installed on it.  This system is excellent if you have a set of detachable flip up iron sight you’d like to use.  

For example, I love my XS Troy CSAT AR sights, so with a railed gas block, I can equip these night sights on my gas block.

at Brownells

Prices accurate at time of writing

Prices accurate at time of writing


Now what about clamp or set screws?  I personally like clamps since they probably more evenly distribute the stress onto the barrel.  But if you really want to make sure your block doesn’t move…dimple your barrel (if it isn’t already) and get the set screws.

How to Tune an Adjustable Gas Block

So this is a very simple process.  Depending on your gas block and rail system you may want to leave the rail uninstalled.

This sounds crazy but you have to be able to adjust the gas block.  Wear some gloves, and hold the mag well.

Accuracy isn’t the major issue here so a solid shooting position isn’t needed.  If you can reach your gas block and adjust it with the rail system in place then do so.

Grab the load you plan to shoot the most through your rifle, or the load that will be most important in your rifle.

For example, if you hunt with your AR 15 you want to tune the rifle to your hunting ammo, and not your plinking ammo.

Hiccups while plinking isn’t an issue, hiccups while hunting can be.

charging bear
Pictured: a potential issue.

Make sure you know which way opens and which way restricts gas flow.  I would start with it opened to allow maximum pressure.

Load a magazine with one solitary round and test how it cycles.  You are looking for two things, how reliably the round cycles the action and if the bolt locks to the rear with an empty magazine.

If the weapon cycles perfectly and the bolt locks to the rear restrict the gas flow by a ½  turn of the adjustment screw.

adjustable gas block adjustment screw
This little guy, if you’re having trouble.

Repeat loading one round per magazine and firing, observing cycling and the bolt locking to the rear.  Restrict the gas system another ½ turn.

Rinse and repeat until the bolt does not lock backward on an empty magazine.  At that point open the gas system ¼ turn.  Repeat the test.

If it locks back that is your optimal gas setting.

If the bolt still fails to lock to the rear open adjust the system another ¼ turn, and this is your optimal setting.

Run a magazine through the weapon and ensure it cycles reliably.

At this setting, the rifle will cycle with the least amount of recoil, and place the least amount of wear and tear on your internals (and your shoulder).

And now the part you’ve all been waiting for (or the part you skipped straight to): our recommendations.

Best Adjustable Gas Blocks

1. JP Enterprises Adjustable Gas Block with A2 Front Sight 

This is just an upgraded version of the standard A2 style front sight that has served the military for generations.  It’s well made, rock-solid in design, and co-witnesses perfectly with most other optics.

2. Superlative Arms Adjustable Gas Block

Best Adjustable Gas Block
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

This adjustable gas block also offers a bleed off hole to reduce gas blowback when rocking a suppressor.

Be sure to check out our complete Superlative Arms Adjustable Gas Block review as well!

What’s your take on the Superlative Arms?

Readers' Ratings

4.98/5 (619)

Your Rating?

3. Seekins’ Adjustable Gas Block

This is for a more affordable option.  It’s what I used to run in previous rifles but sometimes my handguard configuration wouldn’t let me reach the gas detent.  Plus…it doesn’t have the bleedoff option.  But if you’re looking for a plain Jane block that works…the Seekins is great.

at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

4. Double Star Pic rail adjustable gas block

Picatinny Railed Gas Blocks allow you to utilize any front sight that’ll attach to a Picatinny rail.

at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

Take this Block and Adjust It

An Adjustable gas block is slightly more expensive than a regular gas block, but it does so much more.

This is one of the most important parts of your rifle.  I don’t think it will be long until adjustable gas blocks will the be standard among manufacturers.

What do you think?  Was this helpful in your quest to find the perfect gas block? Speaking of accessories that should be standard, you need a red dot or optic. Our list of Best AR-15 Optics & Scopes will help you find what is right for you.

A Couple AR-15 Optics
A Couple AR-15 Optics

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27 Leave a Reply

  • Commenter Avatar
    Johann Mynhardt

    Super informative! Thank you.

    August 1, 2021 12:29 am
  • Commenter Avatar
    Ron Roberts

    The 300 BLK is quite popular among my friends, and I think I will be experimenting soon with the 277 Wolverine. Both of these chamberings have loadings with a heavy bullet or a light bullet, so that fact brought my research to adjustable gas-blocks. This article is the best description of the why and how. I will be looking for more articles that you have written on the AR15 platform.

    November 1, 2020 7:31 am
  • Commenter Avatar
    MJ Sidell

    I am working on my first LR-10 build. Will these blocks work for an 18" rifle length tube?

    October 20, 2020 11:51 am
    • Commenter Avatar
      David, PPT Editor

      Yes, gas block doesn't care about tube length -- just make sure you get a block that fits your barrel's shoulder size and you're good to go!

      October 20, 2020 11:55 am
    • Commenter Avatar
      Jorge Leon

      I use the JP adj block 7 clicks for the 168gr in a 24" bull barrel.

      May 24, 2021 5:14 pm
  • Commenter Avatar
    Tim Whitsel

    I just acquired a new DPMS Mod A-150 chambered for a .204 ruger. The rifle shots well but there is an excessive amount of carbon build up. Would I benefit by changing the factory Gas block to an adjustable gas block. And if so, which type, pinned or set screw? What Mfg would you recommend. Thanks

    October 17, 2019 6:30 pm
    • Commenter Avatar
      Bobby Breidhaupt

      I personally like the Wilson combat adjustable gas blocks. Superlative makes a good block too.

      I don't find much difference between pin in or set screw. As long as you have your barrel dimpled and torque the set screws properly with blue lock tite they are not coming loose.

      Clamp on gas blocks work really well too. There are many good adjustable options available.

      December 29, 2019 9:44 am
  • Commenter Avatar
    Connor Haughton

    Any experience with the PSA adjustable gas block?

    It's a bit hard to justify a $90 upgrade if you're running a $450 rifle to begin with... $40 seems much more appropriate for what literally amounts to adding a set screw to partially block the gas port.

    September 23, 2019 12:34 pm
    • Commenter Avatar
      Eric Hung

      Not yet but we have their new gen of AR-10 incoming that has an adjustable gas block.

      September 23, 2019 2:37 pm
      • Commenter Avatar

        Any word on this PSA part yet?

        April 16, 2020 11:21 am
  • Commenter Avatar
    Jae Fernandez

    You should consider Odin Works 20 position gas block for a low profile AGB. I've used 7 different AGBs, including the ones listed here, and the Odin was the best. Low enough for even BCM'S SLIM handguards, 20 solid and tactile detents, and adjustable from the front.

    July 24, 2019 9:40 pm
  • Commenter Avatar

    Our locally made adjustable gasblock with no tools needed for adjustments. With fron idle control.

    March 11, 2019 10:30 pm
  • Commenter Avatar

    Is there a gas block for the AR-10 that is similar to what some SKS's have, a simple on/off that allows you to manually cycle the action? Would this be beneficial for long range accuracy? Would it help with suppression?

    August 2, 2018 4:57 am
    • Commenter Avatar

      Already tested in NRA article. Difference is very minimal once you are in rifle length, like 20 fps. And rifle length is what you get for long barrels.

      November 4, 2018 4:30 am
  • Commenter Avatar

    Is there any gas blocks that have predetermined setting for suppression. Like you find on say the Scar?

    March 17, 2018 6:34 pm
    • Commenter Avatar
      Matthew Collins

      There are a number of gas blocks that have suppressor specific settings (the Noveske Switchblock and some Odin Works offerings spring to mind first) but most these days are going to have a finer range of adjustment than just "suppressed or unsuppressed" so you can tune your specific rifle and load to get the optimal results.

      March 20, 2018 9:30 am
    • Commenter Avatar
      SOF Arms

      Primary Weapons Systems has a 3-setting gas block for unsuppressed, suppressed with subsonic ammo, and suppressed with regular ammo.

      January 26, 2019 10:22 am
  • Commenter Avatar

    I was just wondering if the superlative adjustable gas block will fit with an 18".223 wylde fluted barrel.

    February 4, 2018 9:41 am
    • Commenter Avatar
      Eric Hung

      They have all the normal sizes out there: .625, .750, or .936"

      March 6, 2018 2:42 pm
  • Commenter Avatar

    I am trying to find an adjustable gas block for my pencil barrelled DPMS AR-15 Oracle WITH a picatinny rail that I plan to run a suppressor on. There is no such animal. Wonder why since I can't be the only person in the world looking for such an item. Also, which is better, an adjustable gas block with no gas bleed off (like the Sentry 6 clamp on unit offered by Midwest Industries) or one that bleeds the excess gas off?

    January 4, 2018 10:42 am
    • Commenter Avatar
      Eric Hung

      That might be a unicorn gas block. Going pencil already cuts down the field a lot. I like the gas bleed off personally.

      January 12, 2018 5:11 pm
  • Commenter Avatar

    Im running a SLR on a 10.3 in pistol build. .223 wylde 1:8

    July 15, 2017 12:13 pm
  • Commenter Avatar
    Jim M.

    I'm curious to know how gas system length affects gas pressure. Would an adjustable gas block be as beneficial on a rifle length system as on a carbine length system or vice versa?

    June 5, 2017 2:16 am
  • Commenter Avatar
    Felix Serrano

    Thanks for all the info.

    What do you guys think of the Odin works adjustable gas block that comes with thier barrels??

    June 4, 2017 5:34 pm
    • Commenter Avatar

      Odin works state theirs are not for short pistol length ports, etc. Too much pressure and seen them crack.

      November 4, 2018 4:31 am
  • Commenter Avatar
    Chris Blackburn

    Have you tested the seekins precision adjustable gas block? I'm curious if it is a quality part. I haven't seen many reviews or videos for it. But this item is available at my local gun shop.

    May 25, 2017 5:23 pm
    • Commenter Avatar
      larry schexneider

      it is a good one. i use it on all my builds. never had a problem yet.

      December 26, 2017 10:12 am