Should I use an adjustable gas block?

[BravoMike]

I am building a SPR/varmint hunting AR-223 with a White Oak Armament 18" SPR barrel with mid-length gas and chambered in 223 Wylde. I wanted to buy the rifle length version but it was sold out during their black Friday sale. I plan on shooting 60gr for varmint, 77gr for precision and shoot mostly suppressed.

The benefits as I understand it with adjustable gas blocks is they provide softer recoil, less gas/dirt back into the chamber and also slightly more FPS since more gas is going down the barrel.

The negatives I can think of is that it will put more gas/dirt down my suppressor and I have read the adjustable gas blocks need to be cleaned periodically. I would rather not pull my hand guard off to clean the gas block. They are also much more expensive than standard gas blocks. I am also concerned about reliability and know there are newer designs where you don't have to worry about the nut walking out (eg odin and slr).

I have never used an adjustable gas block before and am wanting to hear feedback from others who have. How noticeable is the difference in carbon build up in the chamber/BCG? How noticeable will the difference in perceived recoil be? How often have you cleaned your adjustable gas block and have you experienced any failures with it?

 

[jinks]

I use a Superlative Arms adjustable gas block on a suppressed .308 AR. It took a little time to adjust but it is able to fire with or without the suppressor. Superlative Arms bleeds the gas out the front so there should not be additional carbon in the system. I have not cleaned the gas block but I have only fired several hundred rounds.

From: https://www.brownells.com/rifle-par...ampaign=itwine&utm_medium=affiliate&source=ir

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.

Data:

• Gas Block Material: 416 SS
• Barrel Diameter: 0.750"
• Weight: 1.68 oz.
• Length: 1.00"
• Attachment Type: Clamp on
• Gas Adjustment: 30 Locked Positions, Front Of Block
• Bleed Off Port: Front Of Block

 

[mammynun]

My comments will be in reference to an 18" rifle length gas system .308 AR with a Gen 1 Syrac adjustable gas block and a standard rifle length buffer system...

I can make my rifle shoot very softly and still be reliable, but only for a specific load and configuration. IOW, if I set it up to shoot suppressed 175gr FGMM, I will have almost 100% failure to eject shooting surplus 7.62 147gr unsuppressed. Set up for surplus 7.62 FMJ unsuppressed makes 175gr FGMM suppressed way over gassed. If you don't mind sticking with one configuration or changing your gas settings, adjustable gas blocks work very well to reduce felt recoil and reduce gas to the face. I've found that if I set the GB to where suppressed surplus ammo gets ejected about a foot, then FGMM is 100% reliable (with or without the suppressor). The trade off is a little more felt recoil and gas face with FGMM and about a 10% FTE with unsuppressed 7.62 surplus. The gen 1 Syrac requires you to depress a detent while turning a hex head screw, so it's kind of a PITA. I also discovered that whatever position I had last shot it never seemed to be the position I wanted this time, so I settled for the best worst case setting.

I have shot somewhere around 2k rounds and haven't cleaned it; it still adjusts without any issues.

Since you're shooting 223, my experience with 308 may apply less or more, but I would think the physics still apply.

 

[harveyspecter]

What barrel?

I've never had to use an adjustable gas block and until I have problems, I never will. I have a DD MK18 upper (10.3") with a Spike's T2 buffer and run suppressed 75% of the time. PRI Gas Buster charging handle too. Never noticed gas to the face and its run flawlessly on large variety of 5.56 ammo and Hornady .223.

 

[BravoMike]

Thanks guys for the insight. I would think an adjustable gas block for a 308 would be necessary. I do, on occasion, get gas blown in my face but that's only when I'm shooting multiple shots or if the wind is blowing the right way.

That Superlative Arms bleed off block looks intriguing, I may go with that one.