Gas block leaking

[Bantam1]

I have been seeing more carbon around the gas block on my Centurion Arms MK12-ish upper. This is their complete upper with their pinned gas block that they assembled. I have no issues with cycling, but the leaking seems to be getting worse. It's leaking out of the tube and the block. The upper has just under 900 rounds on it so far. I can see the carbon because I painted the upper.

I know the blocks can leak a little, although none of the other uppers I have built have this issue. Just curious if this would be considered normal or if I should be concerned. I have seen a slight reduction in velocity (50-60 fps) on my handloads and factory ammo. I checked the bore with my bore scope and there is no evidence of anything wrong in the barrel. The gas port is still nice and round with no erosion from what I could see.

 

[TonyTheTiger]

Got pics? Everyone has a different opinion on what qualifies as excessive leakage.

 

[Bantam1]

Are the pics not showing? I can see all three I posted in the thread on my end.

 

[TonyTheTiger]

Hmm.. No pics on my end.

 

[Bantam1]

Weird. I am using Imgur for the host and I can see them. Not sure what else to do. I attached directly. Maybe this time it will work?

 

[bfoosh006]

To me the gas tube leakage seems excessive. However, I can't say I have seen leakage on a painted / other then black barrel.

Have you considered pulling the gas tube and inspecting it ?

 

[black5.3]

That seems a little excessive from what i have experienced personally as well. Most of the time there is a little leakage when new and it seals itself up around he gas tube where it enters the block. Im interested to see the replies on this one. Can you post a few pics of the underside of the gas block?

 

[TonyTheTiger]

Looks pretty leaky to me. I've had one look like that but not till after 10k+ rounds.

 

[Bantam1]

I wasn't aware of the gas tube leaking until I pulled the hand guard to look at the gas block more. Like I said the rifle functions, just the velocity drop. At first I thought it was the powder lot I was using. I tested them again with the old lot of powder with the same velocity. I suspected it was due to the leaking block but I just don't know.

There is a little seeping on the bottom but not much.

 

[black5.3]

Have you checked to make sure the set screw is still tight? Wont effect how its leaking at the tube but i would make sure its good and snug.

 

[Bantam1]

The set screw is tight and the gas block is pinned.

 

[Primus]

Here is an idea...call whoever built it and send them pics. Let them take care of it instead of speculating.

 

[Bantam1]

I figured if it was an easy fix why not ask here first. There is potential that somebody here had experienced the same thing. I sent an email to them since nothing came up here.

 

[Lowholer]

It looks like normal leakage to me. All my gas guns do the same thing around the gas block and tube. There is a lot of pressure there. If you were having cycling problems it would be something to consider. I have seen the cheap aluminum gas blocks port openings get enlarged because hot gas erodes the edges as well the gas block ports were not aligned perfect and it burns the port in the gas block kind of egg shaped. That did result in cycling issues. I run superlative adj. stainless steel gas blocks on all my guns now. They are awesome. I show leakage all the time hundreds of rounds and no cycling issues as long as I don't change the loads around it is good to go. .2/10 of a powder charge up or down has an effect on cycling in all my ar10 and 15s.Tells me how consistent my gas block adjustments are.I think your leakage is normal but I am no gun smith just a hobby!
Good shooting to you!

 

[Bantam1]

I spoke to Centurion Arms and they said all was good. I have no cycling issues, just a slight reduction in velocity with the same lot of powder. I thought the leak could have been the issue but it must be something else. I'll try a different lot of primers and see if that changes it.

 

[FishinGuns]

You can pull it and bed it if it’s really getting to you.

 

[Herstal 12]

The leaking is a bit much but since the rifle cycles, who cares
Cheers

 

[Bigjake83]

I have been seeing more carbon around the gas block on my Centurion Arms MK12-ish upper. This is their complete upper with their pinned gas block that they assembled. I have no issues with cycling, but the leaking seems to be getting worse. It's leaking out of the tube and the block. The upper has just under 900 rounds on it so far. I can see the carbon because I painted the upper.

I know the blocks can leak a little, although none of the other uppers I have built have this issue. Just curious if this would be considered normal or if I should be concerned. I have seen a slight reduction in velocity (50-60 fps) on my handloads and factory ammo. I checked the bore with my bore scope and there is no evidence of anything wrong in the barrel. The gas port is still nice and round with no erosion from what I could see.

OP GB Leakage bugs the shit out of me as well and it's very easy to fix.

Buy some high temp spray on adhesive and follow these directions.

hi temp spray on adhesive - Google Search

Remove your handguard to access your gas block .

Remove gas block and clean the inside of the GB and barrel area under gas block with some Scotch-Brite and a degreaser cleaner like carburetor cleaner.

Apply the spray-on adhesive in the pattern that I have illustrated for you in the picture.

Apply adhesive in (Red) area first, then slide your gas block to the blue line and stop, then apply the adhesive to the (Purple) area. Proceed with gas block installation by sliding it forward and properly aligning it. Let it sit for 24 hours before firing.

(It doesn't take much, a thin coat will do just fine.)

(Take the time and tape off the barrel and gas block with some blue 3M tape to prevent overspray)

(Always remember to use a sharpie and make indicator and alignment marks before you remove your gas block so when you reinstall everything goes back to how it was because it doesn't take long for that adhesive to start doing it's job)

(Also it looks like the majority of your gas leakages is coming from the gas block gas - tube junction, remove gas tube from gas block and use the adhesive inside there as well I would do this step first before sealing the gas block)

 

[MountainRogue]

Bigjake has a decent solution for the GB. As for the gas tube, something seems out of spec. I would get a new tube. Then if that doesn’t work...send it in. I assume you aren’t using hot home made compressed rounds.

 

[Bigjake83]

Bigjake has a decent solution for the GB. As for the gas tube, something seems out of spec. I would get a new tube. Then if that doesn’t work...send it in. I assume you aren’t using hot home made compressed rounds.

Thanks, a lot of custom rifle builders use spray-on adhesive to seal the gas system I learned it from Les Baer.

 

[Docsherm]

Weird. I am using Imgur for the host and I can see them. Not sure what else to do. I attached directly. Maybe this time it will work?

Have you tried simply replacing the gas tube? They do not last as long as people think. It could be something that simple.

 

[Bantam1]

I would think the gas tube would last longer than 883 rounds.

 

[J-Hon]

@bigjake83 Question about the adhesive: What's it take to remove the gas block after doing this? Heat and a little bigger hammer, or such a pain in the ass you try to avoid it if at all possible?

 

[Bigjake83]

@bigjake83 Question about the adhesive: What's it take to remove the gas block after doing this? Heat and a little bigger hammer.

Yep heat and a BFH.

 

[Docsherm]

I would think the gas tube would last longer than 883 rounds.

The. Gas tube is designed to be a safety shutoff....... kind of. It is a cheap way to shut down the system to prevent critical damage.
I have seen some gas tubes fail with less rounds. It really is one of the simplest parts of the system.

 

[Bantam1]

I agree, but this was never shot rapidly or gotten hot. It could be slightly out of spec. I'll end up replacing it soon.

 

[Docsherm]

I agree, but this was never shot rapidly or gotten hot. It could be slightly out of spec. I'll end up replacing it soon.

When you replace the gas tube let us know if that fixes the problem.

 

[Bantam1]

Will do