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As I read about it; the goal is 1st) reliable function, 2nd) smooth impulse, 3) reduced recoil and wear on the slammin jammin parts.

So there is a balancing act which involves 1) gas port hole drilled by barrel maker, 2) gas block- adjustable? 3) Bolt carrier weight- M16 vs open arse kind, 4) gas system length, longer is better, 5) Buffer weight and spring strength, 6) Boolit/load, 7) Can...arg

That is 7 or 8 maybe even 9 variables depending on how hot you load the smk-77's vs the 55xm193 etc.

To get at the heart of it all; does a syrac gen 2 (linear) adjustable gas block kinda sorta solve ALL the above issues?

I am stumbling through my 1st 6.8 build and I am going to go with M16 bolt carrier and an H2 buffer for starts. Not quite sure about the spring. Vltor A5's are all out of stock as far as I can tell. Mid length gas.



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I bolted one together with a Wilson 6.8 barrel mid-length gas, I used all standard components except it has a stag 6.8 bolt and bolt carrier, I put an H in it and it runs fine. It has a standard low profile gas block but I cannot remember which one I used.


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My 6.8 I used an SLR rifleworks adjustable gas block and H2 buffer and Tubbs flatwire spring runs smooth as butter did have a JP tuned and polished spring but changed to the Tubbs to get rid of the spring noise.

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You mean the A5 parts are oos or just the spring? You can use any rifle length spring with it.


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Originally Posted by Bluedreaux
You mean the A5 parts are oos or just the spring? You can use any rifle length spring with it.


I'll have to take a much closer look at that. You have to have the special Vltor tube for that as well... right?

Is it worth waiting for? Do Magpul stocks fit their tube?


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Originally Posted by jimmyp
I bolted one together with a Wilson 6.8 barrel mid-length gas, I used all standard components except it has a stag 6.8 bolt and bolt carrier, I put an H in it and it runs fine. It has a standard low profile gas block but I cannot remember which one I used.


Maybe I am over-thinking it. First full build so I am trying to sort it all out in my head before going broke on parts swaps. Maybe you only need the adjustable gas blocks on the 308's.

Then there is this noveske switch block for running a can or altogether negating the gas system.

I wish folks would quit making all this new stuff so I could get on with life... LOL

Last edited by Robert_White; 07/26/16.

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Originally Posted by Robert_White
Originally Posted by Bluedreaux
You mean the A5 parts are oos or just the spring? You can use any rifle length spring with it.


I'll have to take a much closer look at that. You have to have the special Vltor tube for that as well... right?


Yes - the Vltor A-5 is designed to run their buffer and spring in their tube. You can change the stocks for any mil-spec diameter stock, but the buffer, recoil spring, and tube should be Vltor.

Blue may know something different on that, I've just seen a few guys locally have cycling issues swapping parts in the Vltors.

I would not recommend the Noveske switch block for what you are doing. The Switchblock uses three settings: no gas, suppressed, and unsuppressed "open". If you need to tune your gas system to operate, you don't have the same ability to adjust the flow as you do with the other gas block options you are looking at. The Switchblock is a good system, but not optimal for your build, JMHO.

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Originally Posted by Robert_White
As I read about it; the goal is 1st) reliable function, 2nd) smooth impulse, 3) reduced recoil and wear on the slammin jammin parts.

So there is a balancing act which involves 1) gas port hole drilled by barrel maker, 2) gas block- adjustable? 3) Bolt carrier weight- M16 vs open arse kind, 4) gas system length, longer is better, 5) Buffer weight and spring strength, 6) Boolit/load, 7) Can...arg

To get at the heart of it all; does a syrac gen 2 (linear) adjustable gas block kinda sorta solve ALL the above issues?

I am stumbling through my 1st 6.8 build and I am going to go with M16 bolt carrier and an H2 buffer for starts. Not quite sure about the spring. Vltor A5's are all out of stock as far as I can tell. Mid length gas.



Here's how I would break down your questions:

1. Gas port - unless you have a machine shop and experience, leave it alone. Most quality barrel brands will be ported correctly enough to run with standard parts, the lower price point barrels tend to be over-gassed (DPMS comes to mind, and JSE bargain barrels), they tend to error that "more" is better.

Buy a quality brand barrel, and you will probably not have to worry about the gas port.

2. Gas block - Yes, an adjustable gas will allow you to tune the gas flow, and the cycling speed of your system. HOWEVER, You need to decide if you what the forearm to cover the gas block or not. The design/size of the gas block will drive your selection of a forearm tube. Some have gas keys on the side of the gas block, some adjust from the front. If you decide to cover the gas block, you'll need to see if the adjustment location is going to be covered or not. I think the Syrac Gen II is a good choice, and will be an easy gas block to cover with a rail with if you go that route. The adjustments should still be easy to get to from the front, unless you get a super long forearm tube.

3. Bolt carrier - unless you see yourself competing for shot times against the clock and other shooters, the full-auto carrier is the easiest to find, and has pretty much become the standard for BCG sales. Most shooters I know with light-weight bolt carriers are competing in 3-gun, and working the shot-to-shot times down by faster cycling. For the average shooter, a bit more mass to hold everything in battery longer, and smooth cycling when tuned correctly.

4. Gas length - yes, longer is better IMHO, and not something to use a lot of brainpower worrying about.

5. Buffer and spring - IMHO, more of an issue without an adjustable gas block than with one. With an overgassed system of any length, and no adjustment to the flow of gas, the only options are mass in the BCG, mass in the buffer, and more resistance in the buffer spring. You gain the mass in the BCG by using the full-auto carrier, and that's about the limit without getting into special parts that aren't cheap. The buffers now come in several weights, but the H series are the most common. An H-1 is a good start, and you have the adjustable gas block to help balance the system.

Springs - a good spring is going to work, since you are building, I'd get the Rock River spring kit for your build, and to have spares if you lose or damage a spring. It will come with every spring in the rifle. The spring market is not my strongest knowledge base, but Jeff and others have quite a bit knowledge on the subject.

6. Bullets and loads - yes, balancing...but, with the gas block, you should be able to "tweak" any issues with the combinations you want to try. Unless you are loading really exotic rounds, what you have listed for your build should work, and allow you the adjustments to make it work as you change loads.

7. Suppressed - aka blowback. Yes, it's a good idea to be able to adjust the gas for a suppressor, but not always a requirement. If it ain't broke... Again, you are going have to put the parts together in your head, research for others shooters using the same set-up and see what their results are. Gemtec makes a bolt carrier for suppressed rifles, and there are others out there. If the can is never going to come off, then setting the rifle up for suppressed fire makes sense. Or if the can is an occasional use, you probably want the ability to adjust your gas.

A suggestion - build your first upper for daily use, and build a second upper for suppressed when you decide if that is the route you want to go.

I've probably missed something, and there other opinions on these topics as well that are valid as well.

Last edited by AH64guy; 07/26/16.
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AH64guy pretty much nailed it.

I will add that most cheaper companies use larger ports because most cheaper users shoot ammo that is not loaded very hot.

I'll also add that after playing with mid length, intermediate, rifle and carbine gas systems, carbine, H, H2, H3 and 9MM buffers, it takes a really picky shooter to tell the worst from the best by recoil impulse when running hot ammo.

My Larue mid length is the only gun I have that runs better with an H2 buffer. Even my Colt carbine gassed guns run H buffers and eject to 4:00 with all but the hottest ammo and then they dump it at 3:00

Shoot more worry less.

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AH64guy...

I owe you breakfast man! Meet you at the Tasty-29 ! The only "American" place to eat left in Northern VA.

Thanks; helps a LOT


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Shoot more, worry less.

I need to put that on a T shirt.



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On a 5.56, carbine or mid-length, fixed gas guns, I'm using an H1 with a Blue Sprinco (slightly heavier than stock) & it works fine with the mildest 223 (PMC Bronze) ammo & 5.56 (IMI) that I've run through them.

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Originally Posted by Robert_White
AH64guy...

I owe you breakfast man! Meet you at the Tasty-29 ! The only "American" place to eat left in Northern VA.

Thanks; helps a LOT


I've been by the Diner several times, but never stopped. Sounds like a place to stop and try.

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AH64GUY,

Excellent review of most all of the important considerations!

I used a Syrac Gen II on my last build and couldn't be happier.
I can set it down to dump the brass 12" out at 4:00 when I'm on the line prone. The guy next to you appreciates that.


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Originally Posted by Robert_White
Originally Posted by Bluedreaux
You mean the A5 parts are oos or just the spring? You can use any rifle length spring with it.


I'll have to take a much closer look at that. You have to have the special Vltor tube for that as well... right?

Is it worth waiting for? Do Magpul stocks fit their tube?


Vltor or other tube made to length. I think BCM makes one.

You have to use their buffer.

Rifle length springs work. I use a Sprinco green spring.

They'll fit, but won't fully close because the tube is longer. They'll stop at one notch out


Originally Posted by SBTCO
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Originally Posted by Bluedreaux
Originally Posted by Robert_White
Originally Posted by Bluedreaux
You mean the A5 parts are oos or just the spring? You can use any rifle length spring with it.


I'll have to take a much closer look at that. You have to have the special Vltor tube for that as well... right?

Is it worth waiting for? Do Magpul stocks fit their tube?


Vltor or other tube made to length. I think BCM makes one.

You have to use their buffer.

Rifle length springs work. I use a Sprinco green spring.

They'll fit, but won't fully close because the tube is longer. They'll stop at one notch out


I've only tried two Magpul stocks (STR and the new MOE SL) on the one AR I have the Vltor A5 setup on, but pretty sure they both close all the way (will verify later), so maybe some Magpul stocks are different than others in some dimension that affects this.


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