What the big deal with Adjustable Gas blocks?

[Wolfdog91]

Ok hope I don't sound like I'm being sarcastic or something but honestly can someone explain this to me ?

So I've never really messed with adjustable gas blocks but I'm. Constantly being told I should start using them . I don't shoot suppressed so just never saw the point. Well I got one for that 22-250 AR10 build I did because alot of folks said the issues with .22-250 in a gas gun where probably from poor gassing . Well I got one off of Grendel Hunter but never ended up using it because that thing worked perfectly with the standard one. So since it was just sitting on the shelf I tossed it on my .22 ARC build ....and after using both a non adjustable and this one.....egh I can't say I see what the fuss is about. I mean I got it tuned to give a good 3' O'clock ejection... But other then that I really don't feel anything different if anything I feel more recoil then with a standard non adjustable... Is it because I'm a non suppressed shooter or is there just something I'm over looking ? Thanks

 

[Big Mc]

Ok hope I don't sound like I'm being sarcastic or something but honestly can someone explain this to me ?

So I've never really messed with adjustable gas blocks but I'm. Constantly being told I should start using them . I don't shoot suppressed so just never saw the point. Well I got one for that 22-250 AR10 build I did because alot of folks said the issues with .22-250 in a gas gun where probably from poor gassing . Well I got one off of Grendel Hunter but never ended up using it because that thing worked perfectly with the standard one. So since it was just sitting on the shelf I tossed it on my .22 ARC build ....and after using both a non adjustable and this one.....egh I can't say I see what the fuss is about. I mean I got it tuned to give a good 3' O'clock ejection... But other then that I really don't feel anything different if anything I feel more recoil then with a standard non adjustable... Is it because I'm a non suppressed shooter or is there just something I'm over looking ? Thanks
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If it ante broke don,t fix it..

 

[jds holler]

I don't think ya need one -- unless you need one. I haven't needed one yet, so I haven't installed the one I've got either. From what I've heard they may be more problematic than standard, and who needs more problems.. jd

 

[Knotwild]

I think the original stated reasons were using it on barrells with oversized gasports and to reduce back pressure on suppressors. I’ve got a couple, but until now, I was the only one who knew it. And no, I didn’t need them.

 

[dellet]

Probably the #1 reason is over gassing and that shows up many different ways. Sadly most of the people who buy them seem to think they will cure short cycling, under gassed issues. They can’t increase gas flow, only restrict it.

If you need a small base die, an adjustable block is one way to eliminate that need. Slowing bolt speed increases unlock time and allows the base to shrink before extraction. Swipe marks on brass is another.

Since bolt speed is slower, you can keep buffer from bottoming out. This generally leads to less felt recoil and faster follow up shots. Often you can drop buffer weight.

With a well tuned system you can actually increase peak pressure and velocity without blowing the case head out, eliminate swipes which happens when the brass is still so tight in the chamber the bolt can’t rotate it so it slips.

Probably 80% of the complaints about an AR being hard on brass relate to over gassing. An AR 15 is over gassed by design. If you are buying “Mil Spec” parts and want a soft shooting rifle, basically you’re working against yourself.

 

[bpd459]

I’m in the same boat as you. If Eugene Stoner believed his AR system needed an adjustable gas block, he would have made it so. I carried an M-16 / AR for 36yrs in uniform, shot Highpower with them for 20+yrs, and still shoot them weekly. Never once have I used or needed an adjustable gas block.
John

 

[JackWolfKnives]

The only one i would buy is the Rifle Speed. It is a well engineered robust unit. Its need, in my opinion, is application dependent. I can see it useful for:

300 Black AR switching between subs and supers, to choke down the gas to prevent the supers from besting up the gun.

308 gas gun as the variety of factory ammo out there can really vary in port pressure. So I would opt for a large gas port and choke down gas as needed depending on the ammo I’m using. Although not really helpful if you standardize on one specific load.

Otherwise I prefer not to have the added complexity, weight and cost.

 

[effendude]

I shoot a bunch of AR-15's, usually suppressed for prairie dogs. When suppressors became legal in MN, several internet whiz friends told me I needed adjustable gas blocks. I figured if it works, don't worry about it. I am probably overgassed as my mags and BCGs become dirty fast when shooting, but I've never had an issue. I do run the Tubb's Carrier Weight System in a few of my AR's because when I shot OTC, we were running the 80's pretty hard. I wish Tubb still made the CWS system, I'd have them in every rifle.
Scott

 

[6BRA]

Some of the adjustable gas blocks can limit gas or bleed gas. An oversize gas port plays hell on a BCG. Bleeding gas will reduce velocity and soften recoil stroke on bcg. Pistol uppers are hard to get adjusted when running in auto or binary modes. These will also help save benchrest type brass another adjustment besides different buffer weights. Dent prevention. Several purposes. Stoner built 1 version..lots of variants out there with different bbl lengths and gas pulses. Jmo

 

[Canuckienns]

Probably the #1 reason is over gassing and that shows up many different ways. Sadly most of the people who buy them seem to think they will cure short cycling, under gassed issues. They can’t increase gas flow, only restrict it.

If you need a small base die, an adjustable block is one way to eliminate that need. Slowing bolt speed increases unlock time and allows the base to shrink before extraction. Swipe marks on brass is another.

Since bolt speed is slower, you can keep buffer from bottoming out. This generally leads to less felt recoil and faster follow up shots. Often you can drop buffer weight.

With a well tuned system you can actually increase peak pressure and velocity without blowing the case head out, eliminate swipes which happens when the brass is still so tight in the chamber the bolt can’t rotate it so it slips.

Probably 80% of the complaints about an AR being hard on brass relate to over gassing. An AR 15 is over gassed by design. If you are buying “Mil Spec” parts and want a soft shooting rifle, basically you’re working against yourself.

Good explanation, saves me the writing .
Long time builder of high end Ar15, AR10 platforms. Not all are plug and play

 

[Eagle1899]

An adjustable gas block(especially a gas bleed style) can play a very large roll in tuning IF you are outside the normal set up. Suppresors, lightweight bolt carrier, lightweight buffer, + gas systems, large case capacity or subsonic.

 

[spencerhenry]

I have an AR10T that I bought about 25 years ago. It is capable of great accuracy, one ragged hole on many occasions. However, from day 1 it was hard on brass, as in ejector smears, expanded case heads, and blown primers. The loads I was shooting were not particularly hot, but everything looks like high pressure. Armalite told me that I could not shoot reloads, who buys an AR10T to shoot factory ammo? I decreased the load and it helped but did not fix the issue. The load was not the problem, so the rifle went back to Armalite, they bushed the gas port down. Its been a couple decades so I am not sure if I remember the numbers right, but IIRC the gas port was .085 and was bushed down to .063. I got it back and it was better, but still ruining brass. Back in those days no one made a 7/8" adjustable gas block, so I modified the one I had by drilling a hole through the side of the block into the gas tube, then threading the hole making a stainless screw to restrict gas.
It took only a couple rounds to get it dialed in to have just enough gas to function. It was no longer destroying brass. Ejected cases ended up at 4:30 about 6 feet away. Years later I threaded the barrel for a suppressor, I do not recall needing to adjust the gas block.

Many people at the time told me I needed a stiffer recoil spring, or a heavier buffer. To me that perhaps could have cured the symptom but not the disease. The bolt had so much gas that it was opening while the pressure was still very high, every case head was expanded. Ejector smears were horrible often with burr of brass at the end of the swipe. Often the primers ended up loose in the lower receiver jamming up the trigger. It was simply too much gas, or at least that's what I concluded.

 

[dfrosch]

Many barrels have too large of a port. I think manufacturers would rather over-gas and ensure it cycles than take a chance that it doesn't cycle. If it's over-gassed enough, the buffer will bottom out in the tube. This will produce slightly more felt recoil.

With an adjustable gas block, you can tune the load/rifle to where the BCG travels far enough to pick up a round from the magazine, but less than enough to bottom out the buffer. This will make for a very smooth shooting rifle.

 

[David Milisock]

Ok hope I don't sound like I'm being sarcastic or something but honestly can someone explain this to me ?

So I've never really messed with adjustable gas blocks but I'm. Constantly being told I should start using them . I don't shoot suppressed so just never saw the point. Well I got one for that 22-250 AR10 build I did because alot of folks said the issues with .22-250 in a gas gun where probably from poor gassing . Well I got one off of Grendel Hunter but never ended up using it because that thing worked perfectly with the standard one. So since it was just sitting on the shelf I tossed it on my .22 ARC build ....and after using both a non adjustable and this one.....egh I can't say I see what the fuss is about. I mean I got it tuned to give a good 3' O'clock ejection... But other then that I really don't feel anything different if anything I feel more recoil then with a standard non adjustable... Is it because I'm a non suppressed shooter or is there just something I'm over looking ? Thanks
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I have no need, but there are some who have screwed systems and do need.

 

[ELR LVR]

As other's have said, and also what I have read about most all of them is they are over gassed from the factory
I mean if you think about it, they want to ensure cycling of all ammo right
there's only one way to ensure that
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I started using them myself as a means to tune where my brass ejected
Should be at your 3 O'Clock, 2 to 6 feet away, if not you can tune this in also
Also using things like a Heavy Buffer is more of a band aid fix for tuning and using the right size gas port is more the proper way to tune for your particular Gas Length System
Carbine, Mid, Rifle
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Once I used one I was hooked
it is not the sort of thing you need to mess with once you tune it to your rifle
and with the ammo you will be using
Set it and forget it sort of thing, for myself anyway
They can be tuned down so low they short stroke, so you must tune it to cycle with the lowest power velocity / ammo you will ever use to ensure it fully cycles
from there on up consider it over gassed, since any more pressure is a waste
but not nearly as overgassed as without the adjustment. so it tunes it down quite nicely
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I did have one issue with an AR-10 kept breaking the Bolt Catch/Release
After some troubleshooting I figured it was over gassing so much - That the Buffer was bouncing back so hard it still gave the bolt enough inertia to break the bolt catch/release latch.
I installed an adjustable gas block as my first means of addressing the issue since they help mitigate felt recoil and muzzle jump as well
And problem solved, no more broken parts
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The recoil aspect is - when they are over gassed, as all of them are
The buffer slams back against the end of the tube so hard it creates a hard stop
What you want is for the buffer cushion tip to just barely kiss the end of the buffer tube and let the spring itself send it back home, not the recoil of bouncing off the end of the buffer tube.

 

[dellet]

An adjustable gas block(especially a gas bleed style) can play a very large roll in tuning IF you are outside the normal set up. Suppresors, lightweight bolt carrier, lightweight buffer, + gas systems, large case capacity or subsonic.

Thats absolutely true, but let’s look at the “normal setup” or operating expectations.

The rifle as well as the ammo is designed to operate flawlessly in a temperature range of about 175*. It needs to cycle 800 times per minute with the chamber packed with sand, ice or bamboo shoots for 1500 rounds between cleanings. All the while being able to hold a very precise 2 MOA out to 500 yards. (Possibly some exaggeration, but not really).

To do that, by design, the gas system was set up to push an over weight carrier and buffer. The buffer system was not designed to tame the gas impulse, the gas impulse was designed to push enough weight, fast enough to chamber a round from a magazine that had been dropped in a mud puddle then stuck in the freezer to dry. Remember the original design had no forward assist, and the ammo was powered by a different powder than actually adopted.

Now that system is being adapted to 147 different cartridges, all only requiring a simple barrel change.

It’s a battle rifle. It was never intended to be fun to shoot, or excessively accurate. Function was the key element in design.

 

[Coyotefurharvester]

I also drilled/threaded the standard GB I used for a 17Rem upper. Not because of brass damage, but brass loss. Shooting prairie dogs, I didn't need it to eject and lose brass(no catcher at the time). Since I have played with the adjustment, with gas reduced the brass is cleaner after firing. And now have several brass catchers.

 

[jds holler]

I've said it before, but the more I hear about these tuning issues, the happier I am with my little cheap-azzesd Anderson carbine. Myself and two buddies got the same one, and simply have none of these issues. I got mine for sub 400 bucks with free shipping, and have never had a hiccup. I changed my butt-stock to the military type, but it came with the appropriate buffer system an still - no hiccups.

My ejection is 3-4 o'clock, and my brass isn't beat to hell.

I think it's cool that there ARE adjustable gas blocks, and I got one just in case. But I have't installed it, and won't unless there is an issue in the future. jd

 

[Olderthan dirt]

I have some guns with them and some without.
If you build an AR and you are trying to get the timing right, there are things you do to get it just right.(different weights in the buffer, bolt carrier and so on)
Or you use an adjustable gas block if it’s over gassed.
If your setup is not ejecting with a standard gas block, adjustable isn’t going to help.
Usually if your running a short barrel setup , with a standard block you will be over gassed.

 

[dellet]

I've said it before, but the more I hear about these tuning issues, the happier I am with my little cheap-azzesd Anderson carbine. Myself and two buddies got the same one, and simply have none of these issues. I got mine for sub 400 bucks with free shipping, and have never had a hiccup. I changed my butt-stock to the military type, but it came with the appropriate buffer system an still - no hiccups.

My ejection is 3-4 o'clock, and my brass isn't beat to hell.

I think it's cool that there ARE adjustable gas blocks, and I got one just in case. But I have't installed it, and won't unless there is an issue in the future. jd

If you “need an adjustable “ you should send the rifle back to the manufacturer.

If you “want an adjustable block” it should be looked at no differently than wanting a better than an out of the box Mil Spec trigger.

There’s really no difference, it’s just a preference.