Good afternoon everyone and thanks for coming back for yet another edition of TFB’s Silencer Saturday, where eye-stinging hot gas can be a way of life – much like working at Taco Bell. Which brings us to today’s topic: non-flatulence related gas regulation. We’ve discussed the issues surrounding suppressing a direct impingement (DI) AR-15 style rifle in the past and among the most popular options of regulating these systems are adjustable gas blocks. However, we have yet to break down the best available gas block options along with their individual pros and cons. So let’s take a look.

SILENCER SATURDAY #88: Best Adjustable Gas Blocks For The AR-15

I. Why consider adjustable gas blocks? Cap and Trade.

‘There is no free lunch’ is the motto of the suppressed weapons world (along with “f*#ck the NFA” and “dude, where’s my stamp?”). Add a device to squeeze hot expanding gasses at one end of a tube and those gases will look for a new way to make it big in the world – like a failed sitcom actor staring at the help wanted sign for the adult film industry.

The result is gas being forced down the barrel, into the chamber and out the ejection port. Or more gas the down the gas tube, speeding up the action, causing possible cycling issues. (we’re back to discussing gas regulation, not that aspiring adult film star). Most of the time having perfectly adjusted gas in an AR-15 will sound quieter at the shooters ear.

II. Suppressed AR-15 Basics

Before we get into the weeds of adjustable gas blocks, I want to review a few points we’ve made in the past about adding a silencer to the DI AR-15 platform:

• You may not need adjustable gas blocks on your rifles.

I’m not looking to indiscriminately spend your money. There is a chance that your barrel, silencer, spring, buffer and ammo all work together in harmony, providing you with a perfectly functioning weapon. Try it out and look for signs of being over-gassed: lots of gas to the face, cycling issues like failure to feed a new round, case ejection patterns at the one and two o’clock positions can all be a sign of too much gas.

• Not all suppressors are equal.

From internal geometry, external dimensions to the diameter of the bore, different models of silencers and manufacturers will alter the way the rifle’s gas system acts in different ways. Some characteristics will make minor differences when shooting suppressed – such as end cap designs. Other characteristics like caliber or forward venting will make more dramatic changes to the way the gun’s system handles gas.

• Not all rifles are equal.

An AR-15 is a system, meaning that everything from springs and buffers to gas port sizes will alter the way your rifle performs when suppressed. One of the biggest variables in an AR-15 firearm is the length of the gas system – pistol, carbine mid-length or rifle – will play a major role in the way it functions with a silencer. However, even the smallest differences – like the barrel’s gas post size – will change a weapon’s behavior.

• Not all ammunition is equal.

Powders, volume, fillers, and projectile weight will all change the way your gun operates, with and without a silencer attached. You should either permanently tune your suppressed rifle for a specific load (not exactly practical) or have a way to make slight adjustments if variables change.

• All of the above, mixed in a blender.

Take any or all of these variables, mix and match, and you will end up with different results. And it gets even weirder on either the summer or winter solstice and full moons.

The main takeaway is that there is no one perfect solution for every suppressed AR15 combination. Prepare yourself for a bit of trial and error.

III. Other Options Besides Adjustable Gas Blocks:

One of the biggest downsides of swapping out gas blocks is the level of technical skill required. While I still maintain that anyone can do it with simple tools, you should consider using a qualified gunsmith if you don’t have enough experience.

Some shooters who opt for a less intrusive solution to their cycling/gas issues will look at adjustable bolt carriers and keys or heavier springs and buffers.

Another option is picking a suppressor that is known for low back pressure. Sometimes this can be achieved by simply using a larger caliber silencer than the cartridge you are shooting – a 7.62mm can on a 5.56mm rifle for example. Other times a silencer is specifically designed to route and vent gases away from the shooter instead of back down the action.

Speaking of tools, here’s a few that you’ll need if you decide to work on gas blocks:

• Geissele Gas Block Punch Kit – Brownells – PSA
• Geissele Gas Block Roll Pin Tool – PSA – Brownells
• Bench Block – Brownells
• Dead Blow Hammer – Brownells
• T-Handle Hex Set – Brownells

IV. Last but not least, let’s break down the good and the bad of adjustable gas blocks.

Pros

• Fine tune a gas system for a particular setup.
• Relatively inexpensive. About $100 max
• Treats the problem of over gassing rather than treating the symptoms.

Cons

• Not drop-in; Requires a moderate amount of gunsmithing
• In most cases adjustable gas blocks will be clamp on or set screw rather than a more secure taper pin.
• May not work with all hand guards.
• Many require tools for on-the-fly adjustments

Picking AR-15 Adjustable Gas Blocks

Years ago I wrote about one of my favorite adjustable gas blocks, the MicroMOA Govnah. Unfortunately, the Govnah is out of production and no longer for sale. The beauty of the Govnah is that it uses a tool-less adjusting slide plate that is simple to push through with the tip of a bullet. Suppressed, push left. Unsuppressed, push right. Weak ammo, push all the way left.

Although I have not had a chance to try it out, the Strike Industries CAGB functions similarly to the Govnah with a few extra settings. My only concern with CAGB is that it may be difficult to adjust under a hand guard. Let’s see if we can get one in house to review.

Strike Industries Collar Adjustable Gas Block

Notable:

• Five settings
• Clamp On
• $99.95

TFB Announcement Here

Traditional adjustable AR gas blocks often require tools to adjust the settings. On top of that, going back to the same settings can be difficult like when switching from suppressed and unsuppressed configurations. Remove the hassle but keep the functionality with Strike Industries’ innovative adjustable gas block.  Using 5 pre-sized settings and 1 closed setting, easily return to the exact same level of gas flow for your direct impingement system. The gas block easily switches position by rotating the collar by hand or while it’s inside a hand guard with a bullet or blade. 

*Use included allen keys for installation. Not doing so may cause set screws to strip. We recommend all parts be installed by a licensed gunsmith. Recommended torque value for the 3 clamp screws should be no more then 25in/lbs.

Features:
– Tool-less adjustment collar
– 6 preset settings for easy adjustments
– Clamp-On mounted
– Fits on all 0.750” gas block journal

Package includes:
1x gas block housing
1x gas block rotator collar
3x clamp screws
1x spring loaded detent

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Superlative Arms – .625″ Adjustable Gas Block, Bleed Off

$ 99.99 MSRP

The Superlative Arms bleed off gas block is unique in that instead of just restricting the gas from entering the gas tube, it vents excess gas out the side. While I’ve shot a suppressed AR-15 that used a a SA bleed off, I wasn’t focused on the performance of the gas block itself. Bleeding off gas can help reduce blowback, but could venting gas to the side decrease suppression?

Luckily, Dead Air Armament’s Lead Engineer Todd Magee has done some formal testing and has allowed me to use his data on the settings of a Superlative Arms gas block. It looks like there is a sweet spot at the 29th setting.

After getting some input from the Dead Air guys, I think we need to get a formal review of this bleed off gas block here at TFB.

The Superlative Arms patented “Bleed Off”, direct impingement, gas block for the AR15 platform adjusts the gas flow by bleeding the gas out of the block instead of restricting the flow like conventional adjustable blocks.  Results:

• The pressure used in the block is reduced only to the amount required to drive the bolt carrier. The remaining gas / pressure are bled out of the block allowing the system to run much cleaner and cooler. 
• Reduction of felt recoil.
• Patented adjustment detent is located outside of the block and therefore no contamination.
• The gas adjustment screw does not restrict the gas flow; therefore there is no erosion or seizing of the screw / no loss of detent due to carbon build up.  Although it is removable, we have added a safety mechanism, which stops you from unintentionally backing the screw all the way out.
• When using SBR’s and / or suppressors the bleed off port allows the excessive pressure to be exhausted out of the block reducing blow back.

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JP Adjustable Gas System

Detent Style – $119 MSRP

TFB’s precision rifle shooters seem to prefer the JP Enterprises Adjustable Gas Blocks for their fine adjustments and retention screw. While I don’t own a JP Enterprise gas block, I do run their Silent Captured Spring recoil system in two rifles and they are very well engineered. I’m confident that the JP gas blocks will perform as advertised.

The JPGS-9D is our minimized small bore design intended to mount underneath many hand guard models on the market. Its two-piece design allows for easier installations even on barrels with pin-and-weld muzzle treatments.

This model features our new click-adjustable detent system for precise adjustments and secure retention of your gas screw. Never lose you gas setting or screw.

Features:

• Click-adjustable detent system for repeatable setup and secure retention of gas setting
• Six clicks per rotation of gas screw for finer adjustments
• Split yoke design for easy installation even on pin-and-weld barrels
• Easy to access side gas adjustment
• Internally retained detent components means no lost parts

Locking Adjustment Style – $79.95 MSRP

The JPGS-5B model is our minimized small bore design intended to mount underneath many hand guard models on the market.

This model also now includes our locking adjustment feature, which consists of an integral brass set screw that can be tensioned against the adjustment screw after it has been set to prevent any migration that might occur.

Full coverage around gas port providing improved seal and better heat dissipation
True clamp-on design with four positive clamping screws
Easy to access side gas adjustment

Specifications:

• Material: 416 stainless
  
• Finish: Black
  
• Weight: 2.25 oz.
  
• Length: 1.28″
  
• Height: 1.40″ (overall), .78″ (over bore)
  
• Width: .89″
  
• Attachment: 6-32 x 1/2″ socket head screws, T15 Torx drive (included)
  (includes 5/64 x 5/16 roll pin for gas tube installation)
  
• Adjustment: 6-32 x 3/8″ set screw, 1/16 hex drive (included) 

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SLR Sentry 6 Clamp On Adjustable Gas Block

Sentry .625″ Clamp On Version – Melonite Finish – $101.99

One of the lightest weight options available is the SLR Sentry line of adjustable gas blocks. The adjustments on the SLR Sentry are definitive and precise, due in part to the heavy duty spring steel and metering crew setup. I’ve had adjustable gas blocks that were supposed to have clicks, but I couldn’t feel them in the field. The SLR has no problem in this department.

• 1.2 oz
• 15-position adjustability from 0 – .125″ port opening
• Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver
• Single tool click to adjust gas metering
• Melonite finish 4140 Precision machined gas block
• Melonite finish 4140 Nexturn Swiss precision metering screw
• Proprietary Alloy Flat Spring with 1400deg temper
• Melonite finish 4140 detent plunger
• USES STANDARD GAS TUBE
• Tool, roll pin and mounting screws included
• WORKS WITH ALL AR15/AR10 HANDGUARDS

Sentry .625″ Set Screw Version – Melonite Finish

$101.99

Note- If you have a barrel with no dimple or one dimple under the gas port either our .400 or .450 set screw spacing blocks will work fine. There is no difference in the blocks just the front set screw location.

• .400″ Set Screw Spacing
• 1.3 oz
• 15-position adjustability from 0 – 0.125″ port opening
• Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver
• Single tool click to adjust gas metering
• Melonite finish 4140 Precision machined gas block
• Melonite finish 4140 Nexturn Swiss precision metering screw
• Proprietary Alloy Flat Spring with 1400deg temper
• Melonite finish 4140 detent plunger
• USES STANDARD GAS TUBE
• Tool, roll pin and mounting screws included
• Works with ALL AR15/AR10 Handguards

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Odin Works Adjustable Low Profile Gas Block

$89 MSRP

The Odin Works Adjustable Low Profile Gas Block is slightly heavier than the SLR option, but is just a slim for those svelte little hipster hand guards. Note that the Odin Works block isn’t made for pistol length gas and “high pressure rounds”.

Odin Works Announcement On TFB

Other gas blocks are tunable, but the Adjustable Gas Block from ODIN Works is truly adjustable and packed with features. Machined from steel and black nitrided for durability. Front facing stainless steel adjustment screw and spring to handle high temperatures. 20 clicks of ball detent adjustment, no set screws needed, simply adjust the stainless screw where you want it and you’re done. Will fit any barrel with .750″ diameter and works with any caliber.

Technical Specs

• Not for use with pistol length gas systems and high pressure rounds.
• Fits inside all ODIN Works Forends.
• Fits .750″ diameter barrels.
• Weight: 2.10 oz (includes detent ball, screws and pin).
• Made from Carbon Steel.
• Nitride finish.
• Stainless steel adjustment screw and spring.
• 20 adjustments.
• Includes detent ball, cross pin, set screws, and hex wrenches.

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SEEKINS LOW PROFILE ADJUSTABLE GAS BLOCK

$59 MSRP

Notable:

$59 MSRP

40 Adjustments

Tool-less field key adjustment option.

Seekins has a couple of options, the slickest one being their “Select” model that allows the user to set the lowest gas setting +1 click, then install a key that allows for tool-less adjustments in the field. The trick will be finding a a hand guard system that will be compatible with the longer key. But I’d own one, no problem.

The Seekins Precision Low Profile Adjustable Gas Block lets you to fine tune your rifle’s gas system for smoother cycling and operation. Regulating the amount of gas used to cycle the action allows tuning the rifle’s operation to a specific load and the use of low mass bolt carriers, buffers and springs to reduce felt recoil. This is critical to allow faster follow up shots, target acquisition and reliability.

SEEKINS SELECT ADJUSTABLE GAS BLOCK

$119 MSRP

The addition of a suppressor, dirty conditions or even switching ammo are all factors that can lead to undesirable gas settings on your rifle.

Our patent pending design was initially developed to fulfill an order in our Government programs which required the ability to run suppressed or unsuppressed in the field.

The Select Adjustable Gas Block allows a near infinite initial adjustment using an allen wrench. To begin, simply turn the gas screw in (reducing gas) or out (increasing gas), whichever you require, and finish by attaching the gas switch for tool-less, on the fly adjustments without losing your initial gas setting.

For suppressor use:

1. Set the initial gas setting with suppressor on so the bolt locks back on an empty magazine.
2.  Add ONE click
3. Attach the gas switch, and position it all the way to the left (this will be the minimum amount of gas you will need).
4. When you want to remove the suppressor simply take it off and rotate the gas switch to the right adding the amount of gas needed to cycle properly un-suppressed.

When you’re ready to re-install your suppressor, rotate the switch back to the left and your good to go.

*Another option is if you are shooting a suppressed .300BLK and want to switch between subsonic and supersonic ammo simply position the gas switch to the left for supersonic and rotate right (to add more gas) for subsonic ammo.

• 40 position fine adjustment

• Tool-less gas selection switch

• Suppressed or unsuppressed

• Melonite coated tool steel

• Available in .750 and .875 DIA

WILSON COMBAT ADJUSTABLE GAS BLOCK

$75 MSRP

Although I have no practical experience with the Wilson Combat adjustable gas block, it appears to be slim fitting and minimalist.

The Wilson Combat Adjustable AR Gas Block replaces a standard AR gas block and allows you to tune your direct impingement rifle’s gas system for smoother cycling and enhanced reliability. Adjusting your rifle’s gas port will lower or increase your bolt’s cyclic rate and tailors your rifle’s performance to your unique needs. This adjustable gas block is useful on match rifles, suppressed rifles and rifles chambered in non-standard AR calibers, especially when shooting a variety of factory and custom hand-loaded ammunition. A simple adjustment of the locking hex screw at the front of the block lets you control the gas volume so you can tune your rifle’s function to your favorite loads. The Wilson Combat Adjustable AR Gas Block is Chromoly steel with a Melonite finish that will easily hold up to high round count shooting and attaches to your barrel with dual set screws.

*Compatible with all standard USGI pattern AR-15 rifles and DPMS pattern LR-308 AR receivers. Requires 1.45″ internal clearance to fit under rails.

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PSA CUSTOM ADJUSTABLE GAS BLOCK

$39.99 MSRP

The budget option in today’s list comes in the form of a PSA gas block. If you are having gas issues but aren’t ready to make a $100 investment, this may be

Tune your rifle to your specifications. Machined from 1144 Steel, the Palmetto State Armory custom adjustable gas block allows you to increase or dial down the amount of gas returning to the bolt carrier group, resulting in a more reliable and consistent feed. Made in America with an unconditional lifetime warranty.

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VOTE NOW:

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Silencer Saturday is Sponsored by Yankee Hill Machine:

Buy YHM silencers and accessories at:

Silencer Shop – Hansohn BrOthers – dead eye gun supply –

Mac tactical

All YHM Products At Brownells

DEALERS: If you want your link to buy YHM suppressors included in future Silencer Saturday posts, email: silencers@thefirearmblog.com

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special Thanks: Mac Tactical