So are adjustable gas blocks for ar15 in 5.56 worth it? Are they reliable? Do they noticably reduce recoil/muzzle climb?

Yes to every question

Imo, only really needed when running a suppressor.

Yeah I love them. Haven't had any long term issues with any of mine yet. Only started using them when I got into suppressors because then it created over pressure and gas in your face. So for me an adjustable gas block is a must when suppressed.

There seems to be a ton of internet nerds and instagram influencers that get all up in arms about proper gas port sizing.

There also seems to be a ton of internet nerds and instagram influencers that will tell you adjustable gas blocks are a failure point. I fail to see how an adjustable gas block can fail except for seizing upon itself. The alternative to adjustable gas blocks seems to be the BRT gas port inserts, which are more prone to seizing, and can be considered seized once installed.

So if you want a cheap, and effective way to perfectly tune any barrel, a simple set screw adjustable gas block, especially when under a handguard seems like the best way to go. My advice would be to break the rifle in, then take some time to set it, and either mark or stake it and not to tinker with it after that.

I am closing in on 10k on a JP adjustable gas block on a 3 gun rifle.

It outlasted a barrel already.  I examined it when I rebarreled and I could see no wear.

A few drops of kroil every 1k round and it stays unseized.  

If you NEVER put any kind of penetrating oil on it, the adjustment can become seized.  If that happens, allow Kroil to soak for 24 hours, and it will move again.


Worth it on competition guns, and on overgassed guns especially suppressed.

You can run on the ragged edge of reliability or you can just take the edge of of a majorly overgassed rifle.

I run SLR blocks on every single rifle I have, large frame and small frame. Never once have had a problem of any sort - they’re bullet proof. Lots of rounds.
Their design was one of the first to get away from hokey set screws without detents, and ball/spring detent designs.
SLRs tension plate works and works well. It’s impossible for the block to come out of adjustment on its own.
Most guys talking about failure points haven’t used SLRs and either just repeat what they’ve heard and / or are making generalized statements based on adj gas blocks from 15 years ago. The ones from long ago sucked bad - I had plenty of them and yeah had failures. Times changed quite a while ago. Even SLR has had multiple generations and the current gen has been the same for many, many years.

SLR on a few, and even a PSA that came with a Grendel upper.

No issues so far.

Hypothetically, I can somewhat see why people see them as a failure point, but I really haven't had that experience at all, nor have any of the other people I know that use them.

I'm sure we can find anecdotal evidence if we wanted too.

I’ve seen too many seize up in classes, on the range, and on personal builds from fellow officers. For this reason, buying a barrel with a properly sized gas port for what you doing is going to be better for 90% of AR owners IMO.

Now, that doesn’t necessarily mean they don’t have a place. I don’t have a ton of experience on large frame AR’s/alternate calibers, so I won’t comment there. For suppressor use? Swapping buffers or springs is infinitely easier.

That being said, it seems to me that SLR has done a really good job of designing an adjustable if you find yourself requiring one. I’ve used one previously and would use another again.

Or if the gas port is too large.

The adjustable gas block will likely increase service life of all your reciprocating components by reducing extra and unnecessary wear. It will reduce the need for cleaning. Reduce recoil, increase velocity of your bullets, and optimize your ejection pattern. It will resolve any potential compatibility issues between barrel, buffer weight, buffer spring, bcg weight, etc without having to buy and try multiple components, likely saving you money.

The only issue I have had with adjustable gas blocks is stripping out the adjustment set screw so be careful about that especially after you've got a lot of rounds through it. Buy Imo, a modern rifle without an adjustable gas block is missing out.

I have a few, and am kind of on the fence.  In my experience; more trouble then it's worth, but work fine as yet another gas-block if you just run them pretty open.  

I've found carefully tuning an adjustible gas system is a great way to short-stroke in the future on a different load. To get reliable functioning on a broad spectrum of ammunition and loads, you basically have to run it wide open, in my experience. Which kind of defeats the point.  After a thousand rounds or so, the thing then get's frozen in place, and can't be adjusted so easily anymore; which also defeats the point.  So if you carefully tune it down for your 1000 round case of M855 green tips; that's great, but prepare to be frustrated if your next case of ammo has to be milder port-pressure wolf-steel; and you no longer have the ability to adjust.  

Some early generation models use a screw system without a set-screw, which can walk loose on you, if not careful.

Overall, for an AR15 in .223; and a middy gas system - I basically don't think there's much point.  Maybe for suppressed usage, there is, but if so, be sure to get an adjustble system that doesn't require screwing around with little allan wrenches.  And get one that doesn't have a reputation for freezing up.

Disagree.  Most all AR barrels can benefit from adj gas blocks.  I always tune using the lightest ammo I run, which over the past 8+ years at least has been PMC Bronze.

I tune until 100% consistent last round bolt-hold is achieved, then adjust 2-3 additional clicks to open.  I have tested this method with filthy rifles with high round counts without cleanings, low lube, in freezing temperatures etc.

Most barrels I have had have benefitted from this.  A few barrels that had gas ports on the small side showed no benefit and I ran the block(s) wide open.  But this has been very few.

There's a lot of variables in play such as buffer tube length, buffer length and weight, spring length, spring type, spring strength, BCG weight, BCG coatings, muzzle device, level of lube, temperature etc.

9 times out of 10 rifles are over gassed to some degree.  And the thought that adj gas blocks are just for suppressor use is silly.  For many, many years I've done "set it and forget it" non-suppressed builds with SLR blocks and never had to touch them after thousands of rounds.  Every one felt like a nicely tuned, soft-shooting set up.

I think 95% of the flack modern adj blocks get is improper use and expectations.  You have to tune with lightweight ammo and allow extra, additional headroom from there to account for less-than-ideal circumstances.

If any of the components in the action change such as BCG, spring, buffer, muzzle device etc, you need to retune the block.

Full-time suppressed guns are easy - same exact situation as full-time non suppressed guns.

The fun starts with suppressed use, as each suppressor affects gas differently and remembering what non-suppressed setting vs suppressed setting for this particular can on this particular rifle, times 10 rifles  can be challenging.  Again, there's a fair amount of "improper use" in these situations and YMMV.  Noveske's switchblock is kind of a crude sledgehammer approach that leans on the "dummy-proof" side, but may or may not be as well-tuned as the rifle could be.

Then there's folks that just don't GAF and don't want to think or deal with any of it and will happily run an over-gassed gun - and that's 100% understandable too.  Keep in mind running adj gas is a great way to reduce gas-to-the-face suppressor use.

Anyone with a frozen in place gas block needs to acquaint themselves with the miracle of Kroil penetrating oil.

Stuff is amazing.  Put on a few drops and let it soak overnight.  Put on a few more drops and gently work the adjustment screw with an allen wrench.

I like JP gas blocks but I don't have anything bad to say about other brands.

I'll have to look into that.  But really, that's getting up there with the expedient ease level of just pulling it off entirely.  That's not really an in-field quick-adjustent, like rotating the gas-selector on an AUG level.  

I break stuff constantly but still haven't been let down by any of my Gemtech carriers.

None of the adjustable blocks on the market are really as beefy as they should be - either in the body or the components.   Ideally something along the lines of a T91 or LMT piston gas block with internals that remove out the front.   A redesigned fixed FSB casting incorporating that would be pretty badass.

i don't know, but i am a new convert to the A5 system and wow it is awesome.

Yes, yes it is.

Big fan.

OAL is it’s only downfall.

Yeah, no they’re not. If you run your rifles hard (and suppressed) they will fail you. I forgot to update that thread but it failed on me a third time so I dumped all my SLR blocks. Here’s the thread https://www.ar15.com/forums/ar-15/Weird-SLR-GB-issue/118-733907/

This

Bingo. I tune the same way, PMC Bronze 55gr.

Most use SLR, I've used them in the past and work great. But I've settled on Superlative Arms GB's. I don't need the bleed, but it's nice to have options.

All on full time suppressed shorties (2 10.5", 1 8".) I prefer the clamp on units..

And Kroil as stated earlier FTW if ever needed. That shit is magic juice!

Thousand and thousands of rounds and I’ve never had that happen. I’m aware of that thread and I’m well aware SLR had a bad run of springs due to a temper problem. Mine, and I’m sure most have been just fine. Don’t spread disinformation on a known defect anomaly. Crap happens to every manufacturer and I guarantee the past temper issue has been fixed.

I prefer the clamp-ons as well and use them whenever the gas block journal diameter and rail allow for them!

Long term the only difference i see is maintenance.   Every few months i rotate the adjustment screw in and out a few times to remove carbon buildup that can eventually seize the screw.

Not spreading disinformation, did you miss where I said even with the new spring it happened to me again? There were also multiple people in that thread with the same issue, it’s a design flaw IMO. The excess gas was bleeding past the adjustment screw pushing the detent outward and bending the spring over time (cumulative). This may only be an issue with severely overgassed setups like mine, but to say they’re bulletproof is disingenuous.
ETA just reread my old thread, the guy with the mk18 that had the same issue had it happen on a slr block that was 4 years Older then mine at the time. That’s not just a bad batch of springs. You take a overgassed rifle, and add a high back pressure can, and I don’t doubt that it could happen with a brand new one in 1000-1500rds.