Explain the Superlative Arms Adjustable Gas Block to me.

[Marksman]

I've got my new gas block installed but I'm trying to understand a couple of the features. It appears that with the adjustment screw turned all the way in, it closes off any gas going through the tube. Then, the starting point is to unscrew it 4.5 turns which allows the full amount to go through the tube with none being bled off. But isn't there a chance to bleed off too much gas such that it won't cycle the bolt fully?

 

[Tiger_Shilone]

I hope you read the installation instructions as you need to be .025” off the barrel step to properly align the ports on block and barrel.

And the instructions also tell you to start at 4.5 turns out as that is full gas to bolt. Check the rifle is operating correctly , you can either start turning the adjuster back in (restricting gas flow) or turning it further out ( bleeding gas to atmosphere. more open = less gas to bolt) to get desired feel. ( typically less bolt recoil feels softer ).

The advantage of bleeding to atmosphere instead of just restricting flow is that , for a suppressed set up , you get less back pressure than you would by just restricting port size.


EDIT ADD: The superlative is a two port gas block with a restrictor screw running through them. When restrictor screw is fully in the block, all gas to both ports is blocked (one port goes to gas tube, the other to atmosphere). As you open the screw the port to gas tube is gradually uncovered and fully open at 4.5 turns. Once you go past 4.5 turns the other port to atmosphere starts to open and gas is now going through both ports, bleeding off pressure instead of restricting it.

 

[hlee]

And yes, you can cause the gun to malfunction by starving it of gas in restrictive mode, or by bleeding too much in bleed off mode.

 

[msgriff]

Long video (30+ min) of the SA AGB function that's pretty comprehensive. The uploader is fairly well known and respected, and is not a shill.

 

[Holliday]

I've got my new gas block installed but I'm trying to understand a couple of the features. It appears that with the adjustment screw turned all the way in, it closes off any gas going through the tube. Then, the starting point is to unscrew it 4.5 turns which allows the full amount to go through the tube with none being bled off. But isn't there a chance to bleed off too much gas such that it won't cycle the bolt fully?

Careful. Supposedly that gas screw has a limiter. While adjusting mine (with just my fingers on the short end, no force at all) I launched that screw down range, never to be seen again. I was doing this with my rail in place with the long end of the alley key, that they supply. Firing and adjusting.

In talking with super’s support, this did not seem to be much of a surprise to them. They had to send me a whole new block to go through the install process again. Before installing this one I ran it out to the limitor and counted the turns in. Now I keep track that I stay off the limiter.

 

[Kocher]

great video… highlighting how it works… i’m a visual learner..

69. FPS increase with restriction versus venting..

So I say that doesn’t matter, but isn’t that the difference between a 20 inch barrel and a 16 inch barrel as far as velocity

 

[Gtscotty]

I haven't really noticed big velocity dips with my SA gas blocks. I suppose the bleed off level and barrel length after the block would affect that though, and I tend to go longer on gas systems for a given barrel length.


If you're going to run a can, this an interesting post by a Dead Air engineer on the effect of bleed off on metering at muzzle and ear.

Adj gas block lowering at ear dB? - AR15.COM

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