Finally got the field test DI video edited. Some interesting findings. Bleed-off does not sacrifice velocity compared to standard non-adjustable DI gas block. DI bleed-off does well with suppressor, like the piston. Warning, is is long. Not for those with ADD.

https://youtu.be/UwHA9pvkgYA

mbell,

I may have missed it, but what is your assessment on why it is quieter with the suppressor and the bleed off setting?  I would assume bleeding off the gasses would create noise as they are now bypassing the can.  Any theories to explain your results in testing?  BTW, I have a kit ordered to use on a .300 AAC SBR that I'm exited to build and try out.  Your videos pushed me from the syrac and adams arms to the SA version.  Thanks for all your work with these.

I did not expect the difference in sound either because of the gases leaking out of the gas block. But if you look closely at the stills in the piston field test you actually see flame coming out of the suppressor on the restrictive setting and none on the bleed-off settings. I believe that the added sound of the excess gas bleeding out of the front of the gas block is less than the added sound when you combing the operation gas pressure with the excess gas. The excess gas is leaving the rifle thru the muzzle and therefore thru the suppressor. More pressure for the suppressor to handle. Like I said this was a surprise to me but has held true for the piston and DI bleed-off systems. I hear through the grape vine that my findings are being confirmed by more professional sound experts with better equipment.

Mbell -



I have not had the chance to watch the video yet. I scanned thru some of it. Hopefully I can sit down long enough to watch it in it's entirety soon. This work computer does not have speakers :(.





POF has a new adjustable gas block called the Dictator. I asked them if it is a bleed off type and their response was "yes". So it seems that Superlative is not alone in venturing down this path.



With your testing and the others you mentioned, these positive results could lead to many new offerings in the future.

 

Thanks remanaz, I am always open to good ideas and suggestions.  :o) Thanks for your input !

What's the deal with mounting .025" from the shoulder, is that common?

I will be interested to see if this fucks up my SDs.

 In a standard set up the shoulder cut in the barrel would hold the end cap for standard hand guards. The FSB or other gas block would snug up against the end cap. Thus the standard gap would be the thickness of the end gap (.025"-.030"). So in general the position of gas ports in barrels and the length of gas tubes is standardized to accommodate this.The size of the receiving gas port in gas blocks is large enough to give significant "wiggle room". So usually it is fine to but the gas block up against the shoulder if you want. The gas tube will be about .030" further into the gas key, if that matters.
 
Now regarding this Superlative Arms piston kit. The instructions are specific and do not depend on measurements of the shoulder gap. You butt up the gas block, with the gas plug screwed ALL THE WAY into the gas block, against a fully seated bare bolt carrier held forward in the upper receiver. Position the gas block here, centered laterally. Then unscrew the gas plug to the first detent. This does result in a gap but not a prescribed measurement. With any piston kit you just need to follow manufactures recommendations and let the gap fall where it may.

Ok, thanks. My others are taper pin set ups. The one this replaces I just butted against the shoulder

Did a test with my plinker 55gr FMJ load at max venting and max blocking set to one click from bolt hold open each way.


Ten shot strings

Max open:
max= 2948 fps
min= 2908 fps
avg= 2927 fps
sd = 12 fps
es = 40 fps


Max closed:
max= 2955 fps
min= 2915 fps
avg= 2937 fps
sd = 13 fps
es = 40 fps


Didn't have any luck with my 90smk load, the reason I bought this, had a failure to extract right away due to torn rim( forgot my 22 cal rod to knock it out).
At max venting the bolt still locked open then went the other way and had the torn rim. I will try the ST-T3 buffer I just got, just a 3oz buffer currently.
Yes it is a warm load in 90 degree temps, I am hoping I can "fix" it with the gas block and buffer rather than change the load.

I have used the TAC 47 Auto Plug on quite a lot of Saiga 12's and work very well. The extra fouling stays out front so it is easier to clean by just wiping it off with a rag. I've often wondered why someone in the AR world hadn't done this yet. Great idea. I do want to see how well it performs and holds up before I jump on the bandwagon, but I really the concept.

I looked at the AA site and some other reviews. I do not see a bleed-off port on the Director gas block and I don't see any information stating that this system uses bleed-off. I looks like a restrictive block with a set number of positions. If anyone else has any more information on this AA Director gas block please let us know. It looks well made.

Mike, I contacted POF directly and asked them if it was a bleed off type. It is always possible that they misunderstood my question.



This is a POF product not Adams Arms. Also I misstated it's name. It is called the Dictator. It is limited on the number of settings though. Many blogs and articles mention it being geared towards suppressor use.

I misspoke in my post by calling it an AA Director. Looking at the POF Dictator I do not see a vent hole. I do not know. It is a new product to me. My understanding is that Tony Russo had or was seeking a patent on the bleed-off AR 15 gas block. I do not know for sure, that was just my impression. In the reviews and descriptions I found on the interweb I did not see any mention of "bleed-off". Now I am really curious.

I am thinking that the person who responded to my email did not understand my questions. I say this because I also asked if it was serviceable, specifically can the gas tube and adjustment controls be removed. They said no. I was finally able to locate a owners manual page for it on their site and ,low and behold, it gives complete instructions on how to break it down and service it.

I have the POF Renegade plus which comes with the Dictator adjustable gas block pinned in place. It is not a bleed off type such as the one in this thread, but is adjustable by restricting gas based on your preference. It's great for suppressor use.

It comes with instructions on how to break it down for service.

ETA: when you contact POF you'll get one of two types: a total dumbass or one who doesn't give a f**k. I had a very bad customer service experience with them and spoke to several of both types in the process. This is why they responded to your inquiry incorrectly.

The bullet velocity loss of this bleed off system vs standard AR gas system is NONE.  The velocity loss of bleed off vs SLR or Syrac set screw adjustable gas block is TOO SMALL TO MEASURE.  The velocity loss of ANY gas system VS a closed off gas port (or bolt gun) will be a MINISCULE 0-30 fps.  

WHY you ask

As a bullet passes the gas port in a RIFLE gas system it is still being pushed by about 19,000 psi of still expanding gasses.
As a bullet passes the gas port in a CAR gas system it is still being pushed by about 32,000 psi of VERY VERY MUCH still expanding and burning gasses.

The bolt carrier sees...........about 500-700psi............yes.......1/64th of the pressure at the gas port of a CAR gas system.  If the carrier saw the same pressure as the barrel or even 10% of that pressure IT WOULD EXPLODE.  FOLKS THESE THINGS ARE NOT EVEN IN THE SAME UNIVERSE.  You guys are debating whether putting a dozen ugly stickers on the hood (screw gas block) of your car vs on the trunk (bleed off)  will affect gas mileage more vs no stickers (bolt gun or closed gas block).

The size of the gas port in the barrel is an ORIFICE.  It restricts the gas coming out the gas port to a SMALL amount of gas.  Also, going from high pressure to low pressure cools this gas some, plus the gas cools some in the gas tube on the way back and sees MUCH friction in both the gas tube and the gas block before getting to the bolt carrier. As gas cools it contracts (shrinks).  Lets say at the adjustable gas block we are getting 1,000 psi out of 32,000 peak available gas port psi and that drops to 500 psi by the time that gas gets to the bolt carrier through friction and cooling.  If the system was GROSSLY overgassed by 25% we will say it started at 1,250 psi at the gas port.  250psi difference vs 32,000 psi is only 1% or so difference.  With SLR and sentry gas block we keep that 1% in the barrel,  With bleed off we blow it out the front.  ITS ONLY ABOUT 1%.

And this 1%  difference has no effect on bullet velocity AT ALL until the bullet has already passed the gas port...you know....towards the end of the barrel.  And on top of all this we are talking about pressure.  VOLUME is critical to this discussion, but it only takes a SMALL SMALL SMALL volume of 32,000 psi gas to produce the small portion of a cubic inch of 500 psi gas needed at the bolt carrier.

Now lets take the powder into consideration.  The powder is burning and CONSTANTLY expanding until the bullet gets most of the way out of a rifle length barrel.  In SBR's the powder is still burning all the way down the tube.  The powder is PRODUCING pressure and volume at a much faster rate than the small orifice in the barrel can bleed it off.  The cooling from the barrel and the expanding area created by the bullet going down the bore do much more to consume gas volume and reduce pressure than the small gas bleed going into the gas block.  Imagine a magic barrel that "catches" the bullet just as it passes the gas port.  DONT YOU THINK THAT THING WOULD KABOOOOM WITH ALL THAT GAS BEHIND THE BULLET HAVING NOWHERE TO GO BUT THOUGH THE GAS TUBE.  

As far as operation between this and other adjustable gas blocks, I say its just another way to solve the same problem.  It has merits of not wearing out from gas erosion so bleed off might be better on pistol length and CAR length gas systems.  I see nothing wrong with bleed off other than carbon under the handguard and possibly some noise around the suppressor.  I also have no complaints about my SLR, SYRAC, MICRO MOA, or $30 set screw gas blocks.  I use the MICRO MOA on my SBR as I feel it can handle the high pressure gas blast better.  My longer gas systems have Syrac and SLR.  The $30 adjustables are on beaters.

It's the all caps that convinced me.

Have you ever been shooting ammo that is supposed to be subsonic but for some reason some rounds are 10-20fps too fast?

Seems like it could help in some situations.

This is nothing new, what doesn't go thru the gas port goes down the barrel.

You are right in that the gas that doesn't go thru the gas port goes down the barrel, but you are wrong that this is nothing new. The very fact that what doesn't go thru the gas port goes down the barrel is what makes this system different. A typical restrictive adjustable gas block restricts the flow of gas out of the gas port as thus as you pointed out that gas stays in the barrel and helps push out the projectile. Now contrast that with this bleed-off system. There is NO restriction of flow out of the gas port in the barrel. To tune your gas pressure to cycle the rifle the "excess gas" is "leaked" out of the front of the gas block.
What difference does that make you say......
1)Restrictive gas blocks add a little muzzle velocity, whereas the bleed-off has the same velocity as a non-adjustable DI gas block, no more, no less
2)That little bit of hot gas that leaks out of the gas block instead of going down the bore and thru a suppressor on the muzzle makes a suppressed weapon quieter compared to a restrictive adjustment.

I tried to explore and define those differences in my review. I have nothing to do with this company but their product IS different in function and that translates to some real differences. The difference in sound with a can was quite a surprise to me. These differences are even more noticeable with their piston kit. I have not done any AR stuff in a few weeks because I've been working on some rimfire stuff. Here is the video on the field test of the DI bleed-off gas block if you want to check it out. It is different.
https://youtu.be/UwHA9pvkgYA

What is the consensus then, this gas block, or the carrier that has the switch on it?

As I posted above, I did have a small difference between full open and  full closed(while being functional), 10fps avg, it is measurable. I am using this for shooting into transonic so any MV change is pertinent. I was happy to see though that it didn't mess with my SD or ES and can just adjust MVs in my solver.

I just got my gas lock in the mail. Now I'm just waiting for the BA Hanson 10.3" barrel to place it on.

put just one on a 11.5" middy for use with a can and it functions well (quieter, cleaner, lower recoil) wth one exception:

the faxon 11.5” gunner mid-length barrel and superlativearms adjustable gas-block (GB) aren’t an acceptable combo

why? because there isn’t enough room in front of the gas-block to fully regulate the adjustment screw

i can’t even get the allen wrench between the GB and suppressor mount (or flash-hider), so it requires removing the flash-hider, comp or supressor mount to make adjustments, a hassle

worse, its such a tight area that the screw is now adjusted so far out that its touching the suppressor mount

yet i'm not able to get the screw out enough to the point that the bolt failed to lock back on an empty magazine

in this case i’m using an AAC 51T FH and to get more adjustment that i needed, the back of the AAC mount had to be ground down to allow the screw to extend even this much

while its better than what i was using before (a DD 11.5” w/ H3 buffer & red springco buffer spring), i do wish i could have adjusted this combo to its full potential

just a heads-up for this particular combination of parts

Just to make sure I understand this right:

You have about 4.5-5 turns in the restrictive zone (4 clicks per turn) where it essentially duplicates the function of the Syrac (which if I recall had about 4-4.5 turns).  Then past that range, you start activating bleed off.
It sounds like you can use it in either mode depending on your concerns and priorities.  If you wanted to you could completely ignore the bleed-off mode.
Same company that actually made the Syrac.
Can't back the screw out too far like you can on the Syrac,
About $10 cheaper.

Am I making any mistakes.

Mike

I went to SuperArms website to check this out.   The "bleed off" gas exits in front of the block.   Fair enough.  Depending on how long your hand guard is, might fowl that up.   Gas blocks can be adjusted for less recoil but with forward gas pressure, that might offset reduced recoil?  I was wondering with some powders, with gas exiting forward, obscure the view some?

Personally, I would rather have that gas pushing the bullet.  I know its marginal, but there is the need for speed.

mm

sounds about right mike. mbell556 does a wonderful job of explaining how it all works in his video 0y02vdDzRUk


.

Great read, and thanks for the video test mbell.

One issue I hope Superlative Arms has already addressed can be seen at 4:14 mark of this video:

https://www.youtube.com/watch?v=dq33yGTyxP8

It would be great if they upgraded the set screw shaft with milled "channels" for the detent to rest into. The video shows a simplistic 4 sided shaft providing no audible or tactile "click" for each setting that we have come to expect from other adjustable gas blocks like Odin Works, etc. Its a bit of a nit pick but seems like an easy upgrade to round out what looks to be the perfect adj gas block for suppressed users.

The Superlative Arms systems I have do have an adjustment screw with channels milled into it. They look nothing like the four sided screw in the video you posted. You can clearly see the design of the screw an about 2 minutes into my shop review video of the DI gas block. I am not sure if the screw in your referenced video is different because it was a difference for .308 or if it was an older design. I don't know but the ones I have for pistons and DI all have the design in the video below with a palpable and slightly audible click each 1/4 turn.

https://www.youtube.com/watch?v=0y02vdDzRUk
 

Thanks mbell. You are right..Tony just replied to my question and he confirmed they upgraded that adjustment shaft design well over 6 months ago.

Given this I am sold on this product. It provides the same useage and performance as all the other restrictive type adjustable gas blocks like SLR, Odin, Syrac but gives you the additional bleed off option, as well as perhaps a better detent location outside the heat and filth of the inerds of the block. All for the same or less money. I think I need a few of these...just need to decide on set screw or clamp on style....

Thanks to all that contributed here.
Tall

Running into this same situation with a Rugged flash hider mount.  

Nathan, I am running the muzzle device without a washer of any type and the screw is hitting the muzzle device.  Maybe once I add an accuwasher or something it will be ok

That was the first thing that popped into my head as well. The bleed off concept is well proven in that platform. The FAL is one of the softest shooting 308s out there with terrific reliability. I own two of them and have never had a hiccup out of either of them once they were dialed in.

is this what you're referring to, nathan?

Precision Armament Accu-Washer Muzzle Device Alignment System

if anyone out there has 3 or 4 of these shims for sale, i'd like to buy them from you (i don't need a whole package of 18 shims!)

I have watched some of Embel's video- too ADD to watch it all but I appreciate the contribution.

I already ordered and received one of these but haven't decided which AR to use it with.

I like the adjustable gas block concept- but I don't like having to use an Allen key and count clicks when switching between suppressed and unsupressed.

With the forward bleed-off, am I to understand that Once I get the settings dialed in, I should not need to adjust back and forth between can and no can?  In other words will it bleed off more gas with the can and thereby compensate for the extra pressure?

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Watch one of mbell's related videos. It clearly shows that there will be different settings for can vs. no can, regardless whether you use the restrictive or bleed off options. This assumes of course that the objective is to supply just enough gas to make the bolt hold open on the last shot fired (which is the reason to use any type of adj gas blocks in the first place). Think about it, a can puts a lot of back pressure into the system. So there would have to be different gas restriction or bleed off settings to hold the bolt open depending on whether a can was or was not used.

Thanks for the response... I did see the video, and I guess I wasn't clear enough in that question and I probably already know the answer.

Assuming that the gas system is tuned for minimum without a suppressor on a standard adjustable and a bleed-off system, there should be less blowback with the bleed-off system than the other type without adjusting when a suppressor is used.  Obviously not going to be minimum functioning without adjustment, but still better than the others.

I have purchased at least one example of each type of adjustable gas block, and will be testing them for this specific use.

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yes, that is what i did, and how i understand it.... and it works well.

i considered adjusting it for the suppressor thus having the lowest-possible gas pressure to still function correctly, but like you, i wanted to be sure it would function perfectly with-or-without, so i adjusted it without the suppressor and can live with slightly too much pressure when suppressed.

You can buy them individually if you do desire.
https://precisionarmament.com/product/replacement-accu-washer-shims/

I put this SBR together, 11.5" Faxon and the sa gas block.  With no muzzle device at all I can't get the screw out far enough to bleed off enough gas to make the bolt not lock back. The screw comes all the way out to where there are no more detents and the spent round ejects and bolt still locks back. The screw is out so far there is no way this will work with a suppressor.  I decided to run it as a restrictive gas block and I can get it to not lock back, then I come out two more clicks and it functions 85% of the time.  The other 15% I am getting a failure to eject the spent round and attempting to feed the next one.  I am running a standard mil-spec bolt with a JP standard SC spring system with a light spring.  I am wondering if the bolt is cycling too fast. I am going to change the JP to an H2 model to see if that helps.

all right! many thnx Darkamek!

ost, I'm probably going to pick one of these up and I want to watch mbell's videos.

Tag, my suppressed BCM 11.5 LW needs an adjustable gas block.

What is the minimum inner diameter of the hand guard needed for a .750" barrel?