Help with Adjustable Gas Block

[waveslayer]

I recently built out my 18" Grendel and finally had the chance to shoot it. I have a Parallax adjustable gas block with a mid-length tube. I screwed the screw in all the way and backed it out 1 turn. when I shot it seemed to be releasing too much gas, the charging handle would come back and kiss my nose, a fun surprise.

I then screwed it all the way in, and it worked good great, bolt would stay open on an empty mag, but then I noticed this...

What is causing this and what shall I do?

[WildBill3/75]

You could try screwing the set screws tighter to clamp it firmer to the barrel and see if that helps any if indeed it is not tight.

To be honest though, that is perfectly normal....all the gas blocks I've seen leak to a certain degree and after a few rounds being fired the carbon seals any voids so it should be a nonissue.

[Tedward]

You could try screwing the set screws tighter to clamp it firmer to the barrel and see if that helps any if indeed it is not tight.

To be honest though, that is perfectly normal....all the gas blocks I've seen leak to a certain degree and after a few rounds being fired the carbon seals any voids so it should be a nonissue.

yup true and that is why I like clamp on GB's. You squeeze it tight and it does not put pressure points on the barrel. Also they will clap and seal tighter without any leaks. But as WB said, the leaks will clog eventually.

[LRRPF52]

You could also Red Loc-tite the gas block in place if you're worried about seeing the normal leakage.

I have a clamp-on JP that I cut down, and made a lightening cut on similar to the way yours is on the sides of the block, however, I haven't seen any gas leakage like that. I attribute that to the clamp-on attachment method. I do have gas leakage from the gas tube hole, but the gun has run reliably for years now on factory and hand loaded ammunition. The only malfs I have had were when I decided to try out 5.56 PMAGs with 90gr TNT, and I ruined some brass that way.

Everything else has run literally 100% for 5 years now.

[explorecaves]

Since the gas block has been addressed, did you ensure your charging handle is fully latching?

[waveslayer]

Since the gas block has been addressed, did you ensure your charging handle is fully latching?

oh yeah I did, it didn't hit me hard, just touched my nose a few times, and I would make sure it was locked to check it, I even replaced it with 2 other latches I had on hand, they all did the same thing.

Sounds like I will use some Red Loctite and tight the screws up good.

[LRRPF52]

I mean bedding the gas block to the barrel with Red Loc-tite, without getting it into the gas port.

What type of upper do you have? Is it a DPMS by any chance?

[montana]

I'm surprised the rifle functioned with the adjustable gas block screwed all the way in. My Syrac's and SLR adjustable gas blocks cut the gas off when screwed all the way in. Which manufacturer made your Grendel barrel?

[waveslayer]

I mean bedding the gas block to the barrel with Red Loc-tite, without getting it into the gas port.

What type of upper do you have? Is it a DPMS by any chance?

Yes I would do it to just the gas block to the barrel. it's a RRA upper. I trued it up as you instructed...

[waveslayer]

I'm surprised the rifle functioned with the adjustable gas block screwed all the way in. My Syrac's and SLR adjustable gas blocks cut the gas off when screwed all the way in. Which manufacturer made your Grendel barrel?

It was from XCR's Group Liberty buy.

[montana]

It was from XCR's Group Liberty buy.

Where is your brass ejecting while shooting? Towards the front 1:00 o'clock side, 3:00 o'clock, or 5:00 o'clock back? If you have severe recoil with the gas block opened your gas port is too big.

[LRRPF52]

Can you measure your gas port diameter before installing the block. I'm kinda curious what port was used.

[cst]

All gas blocks leak. You wouldnt notice it that much if the barrel was black and the block wasnt skeletonized. Make sure your charging handle latch spring is fresh...My GaP 10 rifle usedmto kiss me on the nose too....too much gas I guess.. changed the latch for me and it went away..

the gun should not cycle if its turned in all the way...I think early Syrac had an issue they fixed

[Klem]

Carbon gas leak is perfectly normal and will be obvious on a shiny SS barrel like yours. Especially on a set-screw design (non-clamping).

It looks like you have that block hard up against the shoulders of that barrel. Do you know whether you need a 1/32" gap in front of the shoulders for the gas holes to line up? If they are not exactly lined up it will exacerbate that carbon bleeding.

I am unfamiliar with the Parallax block and maybe you or someone can help me out here but is the block designed to be used with the traditional AR handguards, or hard-up against the shoulder?

[NugginFutz]

+1

A .025" inch gap between block and shoulder is nearly universal, when it comes to port alignments.

[explorecaves]

company page says on the product page there is a removable set screw for that GB to aide in alignment with the gas port.

[waveslayer]

There is a divot on the bottom of the barrel that a screw on the bottom of the gas port perfectly lines up. I will have to remove it and take a look and measure everything. So guys I will have to break away from the wife and kids... TBD

[waveslayer]

[ATTACH=CONFIG]4603[/ATTACH][ATTACH=CONFIG]4602[/ATTACH]

Can you measure your gas port diameter before installing the block. I'm kinda curious what port was used.

I just took it off and it measured .095" the gas blocks opening measures .150"

What are your thoughts and mounting it I lined up the set screw with the divot.

[Klem]

OK, what I'm talking about is making sure the gas holes are lined up perfectly to maximize the efficiency of your gas system and minimize the sort of carbon fouling you showed us photo's of.

Take a measurement of the distance from the shoulder on the barrel to the centre of the gas hole like this;


It should be at the .300" mark like in the specs drawings for a Lilja;
http://www.riflebarrels.com/products/pdf...4_navy.PDF

Then measure inside your gas block to see if it is the same, 0.300" from the end of the block to the center of the gas block hole. If it is then hard up against the shoulder is where it should be, like the divot is encouraging the block to be. BUT, if the distance in the block is slightly shorter, to take into account the thickness of a handguard cap, then it needs to be slightly forward of the shoulder and that divot is doing you a disservice.

Another way of figuring this out is to push the block back on the barrel hard up against the shoulder. Now spin the block 180degrees. Does the gas hole in the barrel line up perfectly with the center of the grub screw hole?

[waveslayer]

So I measured the distance of the gas port, the center and it is .300. From the shoulder of the barrel. I need to do the 360 degree test with the gas block. From the end of the gas block to the end of the gas blocks gas port Is.368"