Adjustable AR Gas Blocks

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Over at AllOutdoor Major Pandemic writes about the benefits of installing an adjustable gas block on an AR-15 rifle

This last weekend, I provided a buddy a side-by-side comparison of his standard AR and one of my AR-15s with an adjustable gas block. His actual quote was, “Holy crap. When can you do that to mine?” Your first experience with an adjustable gas block will be an enlightening one. The near absence of recoil and almost non-moving sight picture is stunning to say the least, in the “Holy crap, why did I not do this before?” kind of way. I maintain that an adjustable gas block is the most significant performance upgrade anyone can make to their AR format rifle.

After my very first JP adjustable gas block, I was sold on the having the ability to tune the gas pressure on a standard direct impingement AR-15 system. The advantages are a plenty: a large reduction in recoil, faster recoil recovery, faster sight picture acquisition between shots, heat reduction at the bolt, and a bit cleaner running.

What are your experiences like with them? Are they worth having?

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Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


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  • Timo

    IMO adjustable gas block is needed only if you are using lightetened carrier or buffer, and maybe with extended use of a suppressor. Regarding suppressors, I´d rather have a switchblock since I don’t use suppressor all the time. Screw-adjustable gas blocks, like JP here, require thread locker to make sure the screw stays put, and this makes constant adjusting difficult. Even with thread locking compound there is a risk the screw will fall.

    If you are running regular bolt carrier and buffer, the benefits you get from adjustable gas block are simply minimal. Instead the risks for having malfunctions induced by reduced gas flow increase a lot! IMHO stay away from those unless you have a race gun.

    • John Doe

      You obviously have no idea what you are talking about! Just kidding. Yes, these are fine for competition use when used with low mass carriers.

      The adjustment screw on my JP gas block has been fine without thread locker. The threads are so contaminated with firing residue, that it has stayed in place. Still easy to adjust though. I wonder why one has to drill a hole on the JP extended hand guard in order to be able to adjust a JP gas block. Are you listening, JP?

    • Timo

      I forgot to mention I´ve two adjustable JP gas blocks on my rifles and I´ve personally had some trouble with the adjustment screw moving and coming out. Also finding out correct settings can be difficult and problems can occur when the gun gets dirty or you switch ammo type. Of course these problems happen only when are taking part in a competition or a shooting course or some other event where relialibity is essential :) Currently in process of switching them to non-adjustable gas blocks even though I use suppressor every now and then.

  • Daniel

    It should be mentioned that while cutting down on the amount of gas entering the gas system does reduce the recoil, you do so at the expense of reliability with a broad range of ammunition. If you reload and keep your components (down to the lot numbers) absolutely consistent and are willing to use only that load, fine. But I would be very wary of using factory/surplus ammo, since you don’t know what changes they may have made between lots.

    A couple of years ago I would have said that factory ammo can be trusted to be consistent (within a particular load), but with the industry shortages over the last couple of years, manufacturers have had to make adjustments to their recipes based on component availability. Remember, they only guarantee that a load is safe and consistent WITHIN a given lot.

    • Cymond

      Precisely. I’m definitely tempted by adjustable gas bocks sometimes but for me adjustable gas blocks turn a fun tool in to a pure toy.

      I believe they’re only really useful for gamer-guns or to correct an over-gassed gun. I would never put one on a defensive firearm, and every centerfire gun I own is at least a little bit defensive (or at least defense-capable). I don’t own enough yet to devote any to being purely recreational.

      • iksnilol

        I must say that I disagree with you a bit. adjustable gas block is good for suppressed use and of course in harsh conditions its nice to be able to open it up some. SOme rifles even have automatic gas regulators (Dragunov SVD comes to mind).

        • Suburban

          The JP gas block pictured is infinitely adjustable from fully closed to fully open. It doesn’t have settings like a FAL gas regulator. If you were to pick up a rifle with that JP gas block, there’s no way to tell at a glance whether it was set for soft-shooting .223 or full-power 5.56mm.

          • beanfield

            The school of thought here is to take some weak ammo (wolf .223) and use that for your baseline. Start with the gas port closed on the lowest setting (least amount of gas). Take a shot and if the rifle doesn’t cycle, open the gas one adjustment (click or quarter turn) more. Continue this until the rifle cycles. Once you find this point, open the the gas port a adjustments more (a few quarter turns or clicks) for variance. You should be good after this with a little bigger for weak loads.

            Most gas piston systems have tool-less adjustments right on the block. It’s about time DI kept up with the Joneses. SLR rifle works is about to release their satellite gas block feature that will allow for tool-less adjustment of their existing gas blocks. It will work even if the gas block sits underneath the handguard. This should make it easy for people who switch between suppressed and non suppressed shooting. http://www.ar15.com/forums/t_3_124/610963_SLR_Rifleworks_DA6__DA7__DA7_R___DA8_and_DA9_Detent_Adjustable_Gas_Blocks__IN_STOCK.html&page=10#i6262402

        • CliffK

          I thought the SVD only had a 2 position manual regulator?
          So far I’ve only run across a gas plug for Saiga 12′s that is a true automatic gas regulator.
          The plug has a spring loaded poppet valve on the end with adjustable spring tension via set screw.
          This allows a certain pressure to fill the gas chamber and any excess is vented off before the piston is blown back.
          The result is that the piston itself sees the same pressure regardless of how much pressure is coming through the gas port.
          You size the gas port to allow for proper operation of the lowest pressure round you’ll be shooting (ie bulk walmart shotshells), then loosen the set screw until it just begins to vent excess and still operate reliably (granted, that’s not precisely how you tune it, but a general idea).
          From there, any pressures over that limit will be vented and overgassing is eliminated.
          A hot loaded slug will vent considerably, but the pressures acting against the gas piston remain the same.
          The end result is that you don’t have FTE’s with low powered rounds, and no overgassing with high powered rounds.
          You still have the option of increasing or decreasing gas pressure with the set screw, if for some reason you’re running in adverse conditions and need a bit more to muscle through fouling or dirt, AND you can turn the entire gas plug off its detent 1/4 turn to block the gas port off completely.
          I’ve loaded walmart ammo, low brass, high brass, various clay rounds, several types of buckshot, solid slugs, and sabot slugs all in the same drum…and it operated perfectly during a mag dump with zero adjustments between rounds.
          When set up correctly, it’s a pretty impressive little plug!
          If someone were to come up with a gas block that could do that on a gas piston AR, they’d have something pretty special.
          Run low or high powered rounds with no adjustment, with or without a suppressor, hot or cold, dirty or clean, always maintaining the perfect operating pressure without user input.
          That’s something that several dozens of high profile gun companies have failed to properly address with gas piston conversions and uppers.
          Plenty of adjustable gas blocks, but self regulating?
          None to be found in the AR world.
          I’m not sure how well it would work with DI systems, or if it would work at all, but it would be something to look into.

    • Sterling Hess

      While I do agree that having it adjusted for a particular load, will make it unreliable with other loads or environments, but what you can do if reliably was a concern in a situation, I would simply just open the gas block all the way up. The rifle wouldn’t be over gassed, but just function as if it had a non-adjustable gas block since the gas port on the barrel is then dictating the amount of gas the rifle gets.

      My gas block though, SLR rifle works, it is easy to tell when it is opened all the way, so this may not be the case with other gas blocks.

      For me, hopefully all my shooting is for fun, and therefor for me, I am very happy having an adjustable gas block, and it makes the gun shoot very smooth.

  • fsfsfsfs

    Is there adjustable gas block for ar-15s which could hold their settings firmly and would not be skrew and locktide based?

    • Timo

      There are models which have a locking screw (for example Seekings Precision) or a locking detent (Syrac Ordnance).

      • Timo

        *Seekins, not Seekings :)

  • Bruce

    I gotta wonder why your sight picture moves around with a standard gas block. We aren’t talking about full power cartridge here. Proper shooting technique will solve your problems without making an ammo sensitive rifle.

    *Rant On* Time and again I see people drop a bunch of money into a gun to make it ‘shoot better’. What they really need to do is make the shooter ‘shoot better’. *Rant Off*

    • José Pulido

      People who are bad at shooting putting effort towards building a better rifle is a waste of time, but building a better rifle is not a waste of time if you know how to shoot.

  • Vitor

    Actually this a must have for american troops shooting super hot M855A1 rounds, that have 63,000psi, out of a M4 with a short lenght gas system.

  • José Pulido

    The only worthwhile adjustable gas system IMO is the Innovative Arms WAR upper simply because it doesn’t limit you to proprietary or specific handguards or rail systems like most gas blocks will, and actually has 2 distinct settings with the ability to cut off gas completely by leaving the selector between settings.

    I think the entire point of sticking with the AR-15 is compatibility with other rifles in the American market, and since the energy in the gas isn’t unlocked until it reaches the gas key(harhar), it only makes sense that that’s where it be regulated. Regulating the gas at the gas port is simply unnecessary for direct impingement.

    I don’t really care for the company, I just think they’re the only ones doing that particular thing right, and would love to see other companies come up with aftermarket devices that can do the same by modifying the upper and gas tube.

  • MOG

    Never noticed an AR-15/M-16 having much recoil to start with. I may be way behind the times tho. It is great to still have choices in any case.