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Discussion Starter #1
My most recent build is this "DMR", it's built around a Wilson Combat 18" Urban Super Sniper 223 Wylde chambered barrel with an SLR Rifleworks adjustable gas block, Magpul PRS stock with a rifle length spring and buffer. BCG is a nickel boron coated full auto bcg. Geissele SSAE trigger and all the rest of the parts are high end stuff.

Took it out to do a function test yesterday. Gas block was adjusted to position 8 out of 15 so it was about halfway opened. Magazine loaded with 2 rounds of Black Hills 77gr 5.56 MK262 Mod1, Fired 1 round, it chambered the next, fired 2nd round, no hold open on empty mag.
Adjusted gas block to position 10 or 15, fired 2 more rounds, same result no bolt hold open on empty mag. I repeated this until i was running the gas block wide open, chambered rounds fine, no bolt hold open.
Decided to adjust the gas block closed and start over then adjust out to a little over halfway open. Fired 1 round, 2nd round fails to feed with the bolt slamming into the case of the 2nd round. I adjusted to wide open with the same result of the 2nd roynd not chambering and getting slammed in the side of the case by the bolt.
Gas block has a thin coat of blue loctite to seal against the barrel so there are no leaks there but I did notice a very small mark on the rail from gas leaking at the gas tube roll pin.
I've built many carbine and mid length AR's but this is the first rifle length. I had put an adjustable gas block on this build because it will be used with my Sandman S. Never tried it on there when I test fired it though.

What's the problem with this thing? Any thoughts or advice will be greatly appreciated!


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New builds will do this sometimes until the little unseen imperfections are worn in. I would move the gas block back to the original position and shoot some more rounds. You can also try a semi auto carrier if you have one. I've had several that I had to start out with the semi auto until things smoothed out. I then switched back to the full auto carrier.
 

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Discussion Starter #3
I took the rail off to try and see if there are any leaks at the gas block. The block itself doesnt show any leaks but as you can see in the pic, there is a leak at the roll pin in the gas tube. Any ideas as to how I could seal this up? I do have another new gas tube and roll pin in the parts bin and a semi auto BCG if needed.
You'll need to click on the pic and zoom in to see the gas leakon the outside edge and inside the rail.


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I always use the permatex form-a-gasket. Can’t remember the part number. It’s a small tube, and the paste is brown. H recommended it once upon a time, and now it’s all I use on gas blocks—both between the block and the barrel, as well as on the gas tube when it gets inserted and pinned into the block. Cleans up easy with brake cleaner, which is a plus.

Are you sure you’re not overgassed? An overgassed rifle can act a lot like one that is under gassed. You say you dialed it down to start over, but didn’t mention if you worked your way all the way back up to full open. Or maybe I’m just not reading that right...

also, did you check to make sure the GB is centered on the gas port? If it’s canted at all, that could be your problem.
 

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Discussion Starter #5
I always use the permatex form-a-gasket. Can’t remember the part number. It’s a small tube, and the paste is brown. H recommended it once upon a time, and now it’s all I use on gas blocks—both between the block and the barrel, as well as on the gas tube when it gets inserted and pinned into the block. Cleans up easy with brake cleaner, which is a plus.

Are you sure you’re not overgassed? An overgassed rifle can act a lot like one that is under gassed. You say you dialed it down to start over, but didn’t mention if you worked your way all the way back up to full open. Or maybe I’m just not reading that right...

also, did you check to make sure the GB is centered on the gas port? If it’s canted at all, that could be your problem.
I spent alot of time making sure the gas block was centered correctly, marked the correct position and used an SLR dimpling jig to add a second set screw dimple to the underside of the barrel. I'm confident in its position.
When i started over after closing the gas adjustment, I started at the middle position add worked my way up to fully open. I never tried it at a position lower than half open.
The Permatex form a gasket stuff you're taking about, is it thick, brown and sticky as hell?? I've got some like that at our shop if so.

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Does the hole in the gas tube match up with the hole in the gas block? I’ve had it happen that the hole in the tube and gas block were offset by about half the hole diameter, and that will choke things down.


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Discussion Starter #7
As far as I can remember everything was ok, but I'll check that out too. Thanks

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Wilson barrel makes me think the hole in the barrel needs to be drilled larger based on other people's experiences
 

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Discussion Starter #9
I always use the permatex form-a-gasket. Can’t remember the part number. It’s a small tube, and the paste is brown. H recommended it once upon a time, and now it’s all I use on gas blocks—both between the block and the barrel, as well as on the gas tube when it gets inserted and pinned into the block. Cleans up easy with brake cleaner, which is a plus.

Are you sure you’re not overgassed? An overgassed rifle can act a lot like one that is under gassed. You say you dialed it down to start over, but didn’t mention if you worked your way all the way back up to full open. Or maybe I’m just not reading that right...

also, did you check to make sure the GB is centered on the gas port? If it’s canted at all, that could be your problem.
I was wondering which type of Permatex Form-a-gasket you use? I looked at their website and they show 3 types. One that sets up hard/quick cure, the 2nd stays pliable/quick cure and a 3rd pliable/slow cure. They all are good to 400 degrees.

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If the bolt does not lock back on the last round you are either under gassed or over buffered. If you are undergassed, an AGB is not going to get you more gas to the bolt.
Go back to the basics. Put a standard buffer in. Install a standard gas block. Use a SLR dimpling jig to get the gas port aligned with the gas block. Once you establish that, don't monk with it. Use quality factory ammo to do the testing. If you do not get lock back, increase the size of the gas port one drill size at a time until it locks back,
Wilson barrels are notorious for having undersized gas ports. Also, slightly chamfering the gas port on the barrel will also help Check the gas port and also the gas block for burrs. If there are any clean them up with the appropriate drill size.
 

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Discussion Starter #11
If the bolt does not lock back on the last round you are either under gassed or over buffered. If you are undergassed, an AGB is not going to get you more gas to the bolt.
Go back to the basics. Put a standard buffer in. Install a standard gas block. Use a SLR dimpling jig to get the gas port aligned with the gas block. Once you establish that, don't monk with it. Use quality factory ammo to do the testing. If you do not get lock back, increase the size of the gas port one drill size at a time until it locks back,
Wilson barrels are notorious for having undersized gas ports. Also, slightly chamfering the gas port on the barrel will also help Check the gas port and also the gas block for burrs. If there are any clean them up with the appropriate drill size.
It has an SLR adjustable gas block, it has been centered correctly and I used an SLR dimpling jig too. The buffer is standard rifle length, not a carbine buffer. No leaks at the gas block and barrel but there is a leak I noticed at the gas tube roll pin. As for it being a Wilson Combat barrel, yes I've heard their 6.8 barrels have an undersized gas port. I had not heard of any issues with 223 Wylde chambered barrels which I have.
The ammo used is Black Hills 77gr OTM Mk 262 mod 1. This is the only ammo used.
I'm going to try and seal up the leak at the gas tube and see if that helps. If not, I'll take the AGB off, measure the gas port in the barrel and possibly enlarge it and I may go to a standard non adjustable gas block. As someone mentioned earlier, i may try a semi auto BCG as well. Since mine has a rifle buffer, nothing much i can do there.

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Discussion Starter #12
I decided to take the AGB off and check the gas port size. It's a .093...which seems kinda small. I slid the shaft end of the correct drill bit in the gas port, it went partially in and stopped before going into the barrel. It looked like when it was drilled, they stopped just short. I went ahead and drilled all the way out to .093.
I need advice, should I put it all back together and seal it up as is or drill out the gas port and if so what size? I'm thinking of keeping the AGB , i like the benefits of being able to adjust it down for suppressor use.

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I decided to take the AGB off and check the gas port size. It's a .093...which seems kinda small. I slid the shaft end of the correct drill bit in the gas port, it went partially in and stopped before going into the barrel. It looked like when it was drilled, they stopped just short. I went ahead and drilled all the way out to .093.
I need advice, should I put it all back together and seal it up as is or drill out the gas port and if so what size? I'm thinking of keeping the AGB , i like the benefits of being able to adjust it down for suppressor use.

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I would ask H or Carnby. The good thing having and AGB is of you go a little too big your still ok.
 
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