How do AR adjustable gas blocks work?

[BumbleBug]

I've been reading about adjustable gas blocks for AR's. Don't know if it is a standard on high-end models or an after market add-on for AR aficionados. Sounds like a great idea, but what are the actual mechanics? That is, do they partially cover the gas hole, some type of needle valve, or what??? Also, has anyone found this feature useful.

TIA...

...bug

 

[thedudeabides]

It's essentially a valve which replaces the factory gas block and controls the gas flow, like a faucet. Factory is wide open, this one lets you adjust it--just like the flow of water in a spigot.

You can fine-tune the gas flow until you get no recoil but still get cycling of the bolt carrier. An oversimplification is that the AR design sacrifices recoil for reliability, this lets you dial it down until you jam, then up a bit more and you have one smooth rifle.

You can also smooth things out by getting lighter BGC's and softening up the recoil/buffer spring.

 

[Palmetto-Pride]

You can fine-tune the gas flow until you get no recoil but still get cycling of the bolt carrier.

Uh wrong........you may be able to smooth out the gas cycle a little bit, but there is no way you are going to eliminate all recoil.......that just isn't going to happen

 

[g.willikers]

We know what he meant by "no recoil."
Compared to what many of us grew up with, like 30-06, using the phrase "no recoil" for a .556 AR is ok.

 

[Palmetto-Pride]

We know what he meant by "no recoil."
Compared to what many of us grew up with, like 30-06, using the phrase "no recoil" for a .556 AR is ok.

Oh I thought "no recoil" means none or zero. If he meant reduced or little recoil I thought he would have used "reduced" or "little".....silly me I need to go back and put my nose in a dictionary Apparently I could have gone out with a lot more girls in school than I previously thought.......thanks for enlightening me....had I only known

 

[thedudeabides]

We know what he meant by "no recoil."
Compared to what many of us grew up with, like 30-06, using the phrase "no recoil" for a .556 AR is ok.

Also throw some brush guns into that mix, 308 bolt guns...

A heavy AR shooting 223 or 556 already has soft recoil. Once you introduce an adjustable gas block and handloads it's minimal, essentially not even noticeable.

Properly optioned and set up, there might as well be no recoil. A rifle like that can be shot until the barrel cooks without your shoulder being a bruised mess the next day.

 

[oryx]

In one sentence your saying that the AR already has a soft recoil, and the next your saying with a properly optioned and set up one you can shoot all day without your shoulder being a bruised mess.

You can take a standard AR and shoot it all day long without bruising. If you are getting buried up after shooting an AR, something is wrong. The first time I took my little daughter weighing 70 lbs she put a couple hundred rounds through it and wanted more.

The truth is that an adjustable gas block will will not come close to eliminating recoil. You can shut it down all the way and the gun will still recoil. Softening a recoil impulse slightly is one thing, but it is still noticeable. Even in conjunction with a low mass carrier and custom tuned springs it will still be only reduced.

AGB's are an affective option for the intended purpose, but not a miracle recoil reducer

 

[Willie Lowman]

The point of an adjustable gas block is not to reduce recoil.

It is to allow the right amount of gas back to the carrier for reliable function without

1) over gassing. Causing the BCG to move to quickly causing excessive wear on the rifle and possibly malfunctions

2) under gassing. Causing the BCG to not move with enough force to properly cycle and cause malfunctions.

Some competitive shooters and hunters like adjustable gas blocks as it lets them tune the rifle to their hand loads. Some suppressor users like adjustable gas blocks because suppressors increase gas back pressure.

 

[Palmetto-Pride]

The bottom line is the only reason you really need an adjustable gas block on a AR would be if your AR was over gassed. A couple reasons for that, but not limited to could be if the gas port in the barrel was over drilled, gas port drilled in the wrong position for length of barrel. The only way to fix a under gassed AR is to drill the gas port bigger.

 

[oryx]

Actually, most of the under gassed guns I have seen are from poor alignment of the gas block or FSB. Correcting the alignment is another way of fixing an under gassed gun. . But, I hear what you are saying and think we are on the same page.

 

[Darker Loaf]

Heh, maybe my flesh is weak, but I get bruising from simply aggressively shouldering a rifle, I've noticed. I always get bruising from shooting shotguns (like 50-100 rounds in a sitting), even target loads. But I'm pretty sure it's not from recoil. I'm just locking my rifle into my shoulder so hard that I get some light bruising (goes away in 1-3 days). I'm guessing it's not from actually firing the rifle/shotgun, because I noticed when I was practicing holding my AR w/o any shooting involved that I would get light bruising. The only gun that's ever bothered me recoil wise was shooting around 20 rounds of .300 Winchester Magnum with just a t-shirt on. That actually hurt bench shooting that thing! Maybe I was just shooting into my collar bone or something, but it's snappy! With winter clothes on the .300 isn't bad, though.


Anyway! That's not what the OP was asking about! How are adjustable gasblocks on AR-15's? I'm getting an M-4 2000 from AAC (hopefully) and plan on throwing it on my Rock River Arms Elite Operator 2. Because I'm running a traditional gas impingement system, I'm anticipating getting a gas buster charging handle, heavier buffer, and/or adjustable gas system. So does anybody have a Noveske Switch Block or a JP adjustable gas system with some experience with it?

 

[BumbleBug]

Thanks for the good responses...

I guess there is a table somewhere that matches gas-block barrel location to hole diameter(?). The adjustable GB seems like a good option for the handloader or tinker that would like to fine tune his AR.

Thanks for the info...

..bug

 

[thedudeabides]

I've always used it to quell recoil to barely noticeable and have faster follow ups for target shooting and taking down varmits... that along with an ultralight BCG.

I guess I'm not using it the way the experts meant it to be used.

 

[BillyJack3]

Don't know if it is a standard on high-end models

For some it might be but for many, it comes down to properly setting up the AR. This is why a barrel is not simply a barrel. Manufacturers can spec the gas port for their set up. When that is done, the system runs well and an adjustable gas block isn't needed.

 

[bitttorrrent]

ok just had hand surgery few days ago and of course brother in law was in town and wanted to go shooting.

ok not an ar, but ruger mini 14in .223 and I shot it with my good arm/shoulder - he helped me prop gun up on bench - with no problem and not much recoil to me and my other hand which I did keep away from the gun.

and it was snowing.

so if you think .223 has some kick, you might want to trade it in on a.22!

 

[nadrepadre]

How about on a .308 rifle? I'd rather not sacrifice reliability for a slight reduction in recoil. Lighter BCG and adjustable gas block?

 

[oryx]

Same principles, different caliber. I have the same AGB on both my 5.56 and .308
At the level of reaction from a gas block adjustment only, there is only minor reduction in recoil - and it's from a very slight adjustment in bolt speed. Stop the bolt completely and it's like firing a bolt action - still recoils. Improper adjustment causes short stroking of the bolt carrier and malfunctions occur.
Guns set up for suppression usually have larger porting so they can increase gas to cycle at lower pressures and when firing unsuppressesd the gas block can be regulated down to function without over gassing.
Most guns that are set for up normal operation don't always need regulation and only takes minor adjustments of before short stroking. Generally the gas ports in an adjustable block are larger than normal barrel ports. The result is from wide open on the gas block to the first number of lower settings has no effect on the regulation.