Gas Ring Help!

[Oranga]

I took my new custom build to the range twice now, and both times have left with shredded gas rings.

A little background first, the rifle is brand new, put together by me from parts I’ve gathered all over, the bolt and carrier were assembled by Global Tactical. If you click here it’ll take you to the product description, and you’ll see that the main components are made by CMT. The upper is Mega, the barrel is a carbine length gas system Del-Ton.

I did not headspace the rifle, as the barrel and the bolt were both new and supposedly in spec.

The first time I went to the range, I was shooting Monarch ammo, and after about 10 rounds, the bolt wouldn’t seat all the way, and the firing pin wouldn’t even touch the primer. The second time, after I replaced the gas rings, and cleaned everything out, I was shooting PMC ammo and got through about 25 rounds before I heard a click.

Here are some pictures:

1st time:

2nd:

As you can see, the damage is on the extractor side of the bolt and on the same ring both times. The pictures don’t show this, but the damage is on nearly half of the gas ring, with the other side intact. Also, you can see a sliver of the gas ring starting to shear off.

Also, when I disassembled the BCG, the cam pin took a great deal of force to make that quarter turn, and there is an indentation on the cam pin where it meets the edge of the bolt:

I’ve checked the inside of the carrier, and it looks smooth. Also, the closest thing to a gunsmith at the range suggested it might have been headspace issues, but when he looked at some spent casings, he felt they looked okay. When I said that the rifle was put together by me from scratch, he said maybe I just eff’ed something up, but a cursory once-over of the rifle revealed nothing glaring.

So thats where I’m at, either there’s something wrong with the bolt and/or carrier, or somehow I messed up the rifle during assembly due to my inexperience (this is my first build and first rifle).

One question I have (besides how to fix this) is why is it that only that one ring is getting damaged and not the others?

My next step is to find someone would be kind enough to lend me their carrier to pair w/ my bolt to try to troubleshoot the problem, but in the meantime, I would love to hear some theories on what could be going on. Thanks guys!

[kmrtnsn]

I wish that I could see the rifle in person. That the gas ring has peeled forward, toward the bolt face is really interesting, as are the different score marks on the cam. I wish the bolt were clean before you fired it. Based on the amount of carbon that I see it is hard to say what happened to precipitate this. I am voting toward some kind of over pressure incident but there are conflicting indicators. A early primer hit, perhaps? Firing out of battery, or partially out of battery. Are there any marks in the upper receiver, in the bolt cam track? Powder burn marks? None of these were hand loads, right? I know you didn’t check headspace, but did you check firing pin protrusion before you test fired it?

[markm]

Does the bolt move in and out of the carrier with the appropriate amount of tension?
(before the rings are destroyed) You should be able to push the bolt in and out of the carrier when the BCG is assembled.

I don’t think that Monarch is remotely ammo for anything. But I’ve never heard of ammo doing this to rings.

[bkb0000]

OBDs cause mass destruction… it isn’t OBDing.

did you clean and lube? a lot of FNGs confuse factory cosmoline for lube… that’s not lube, it’s preservative.

i assume you did clean and lube, so- are you sure you tightened the barrel nut down all the way? how did you tighten it (method)?

if these two are check marks, then call Grant and get a new BCG. shit happens sometimes, and if it’s the BCG he’ll take care of you.

[Thomas_M-4]

Something is up with your bolt carrier to shred the gas ring. Can you shine a light down the bore maybe there is a burr some were maybe at the 2 gas ports would be my guess. Also remove the shreded gas ring leave the 2 good ones on there try to insert the bolt by its self and cycle it with your hand can you feel something trying to catch the ring? If you find something wrong with the carrier call denny its usually best to try and call him in the morning.Good luck

I am almost certain that the 2 gas ports have some kinda burr the ring is damaged on the extractor side

[Oranga]

@kmrtnsn

I wish that I could see the rifle in person. That the gas ring has peeled forward, toward the bolt face is really interesting, as are the different score marks on the cam. I wish the bolt were clean before you fired it. Based on the amount of carbon that I see it is hard to say what happened to precipitate this. I am voting toward some kind of over pressure incident but there are conflicting indicators. A early primer hit, perhaps? Firing out of battery, or partially out of battery. Are there any marks in the upper receiver, in the bolt cam track? Powder burn marks? None of these were hand loads, right? I know you didn’t check headspace, but did you check firing pin protrusion before you test fired it?

The rifle was cleaned before both range trips. I looked at the spent casings and the primer hits are right in the middle so that eliminates the out of battery theory. Nothing weird in the upper receiver. I did not check firing pin protrusion. The pin sticks out just enough so that it looks like a half sphere coming through the bolt face.

@markm

Does the bolt move in and out of the carrier with the appropriate amount of tension?
(before the rings are destroyed) You should be able to push the bolt in and out of the carrier when the BCG is assembled.

I don’t think that Monarch is remotely ammo for anything. But I’ve never heard of ammo doing this to rings.

Before the ring got mangled, the bolt did move in and out w/o too much resistance. However, I am new to AR’s and this is the only BCG i’ve handled so I don’t know how much resistance is normal. I can describe it as requiring pretty firm pressure, similar to pushing a plunger on a soap dispenser.

@bkb0000

OBDs cause mass destruction… it isn’t OBDing.

did you clean and lube? a lot of FNGs confuse factory cosmoline for lube… that’s not lube, it’s preservative.

i assume you did clean and lube, so- are you sure you tightened the barrel nut down all the way? how did you tighten it (method)?

if these two are check marks, then call Grant and get a new BCG. shit happens sometimes, and if it’s the BCG he’ll take care of you.

I tightened the barrel nut on my DD Lite rail with the proprietary wrench and a torque wrench set to 50 ft-lbs per the instructions for the rail.

@Thomas_M-4

Something is up with your bolt carrier to shred the gas ring. Can you shine a light down the bore maybe there is a burr some were maybe at the 2 gas ports would be my guess. Also remove the shreded gas ring leave the 2 good ones on there try to insert the bolt by its self and cycle it with your hand can you feel something trying to catch the ring? If you find something wrong with the carrier call denny its usually best to try and call him in the morning.Good luck

I am almost certain that the 2 gas ports have some kinda burr the ring is damaged on the extractor side

Upon closer inspection, there IS a TINY burr in one of the gas ports on the side. However, it doesn’t look like it protrudes into the cylinder that the bolt travels in, so I won’t jump to any conclusions. I’ll try to take a picture, but it will be hard. However, if this is what’s causing the problem, why would it snag only the first ring, and not the others?

[Thomas_M-4]

@kmrtnsn

I wish that I could see the rifle in person. That the gas ring has peeled forward, toward the bolt face is really interesting, as are the different score marks on the cam. I wish the bolt were clean before you fired it. Based on the amount of carbon that I see it is hard to say what happened to precipitate this. I am voting toward some kind of over pressure incident but there are conflicting indicators. A early primer hit, perhaps? Firing out of battery, or partially out of battery. Are there any marks in the upper receiver, in the bolt cam track? Powder burn marks? None of these were hand loads, right? I know you didn’t check headspace, but did you check firing pin protrusion before you test fired it?

Firing out of battery can not happen with ar-15 Ned Christian proved it with a pic of a cut away rifle. Its in a thread looked for it and I cant find it the search function sucks donkey dick. And If he had overpressure there would be signs of it on the brass.

[kmrtnsn]

How many rounds have you fired? There is a LOT of carbon on that bolt.

[Oranga]

@kmrtnsn

How many rounds have you fired? There is a LOT of carbon on that bolt.

I cleaned the rifle in between range trips, so in the second set of pictures, that was after no more than 30 rounds.

[Thomas_M-4]

Upon closer inspection, there IS a TINY burr in one of the gas ports on the side. However, it doesn’t look like it protrudes into the cylinder that the bolt travels in, so I won’t jump to any conclusions. I’ll try to take a picture, but it will be hard. However, if this is what’s causing the problem, why would it snag only the first ring, and not the others?[/QUOTE]

The rings travel all the way to the gas ports they stop even with the 2 ports but they do not go past the port.
Thats why only one ring is getting damaged
I am almost positive its that burr.

[kmrtnsn]

Look at the amount of carbon in the “second stage” (I truly have no idea what to call it, the round narrow “waist” area in the bolt) There is a lot of carbon there, an unusually large amount. I am voting for a timing issue. There is too much gas moving to the bolt (over-pressure). Too small or crimped gas tube, too large a port hole in the barrel, something along these lines.

What are you using for a gas block? Gas tube? Carbine or 20" barrel?

[Thomas_M-4]

@kmrtnsn

Look at the amount of carbon in the “second stage” (I truly have no idea what to call it, the round narrow “waist” area in the bolt) There is a lot of carbon there, an unusually large amount. I am voting for a timing issue. There is too much gas moving to the bolt (over-pressure). Too small or crimped gas tube, too large a port hole in the barrel, something along these lines.

What are you using for a gas block? Gas tube? Carbine or 20" barrel?

Thats gas being blown past the damaged gas rings

[kmrtnsn]

I thought about that but I would expect that carbon to be more localized around the damage in the ring. If you look there seems to be a very even and heavy distribution on the “shoulders” after the “waist” nearest to the cam. I am still thinking that there is an over-pressure/timing issue.

[Thomas_M-4]

@kmrtnsn

I thought about that but I would expect that carbon to be more localized around the damage in the ring. If you look there seems to be a very even and heavy distribution on the “shoulders” after the “waist” nearest to the cam. I am still thinking that there is an over-pressure/timing issue.

Thats blowby from the damaged gas ring. He needs to find another carrier swap it out and test it to be sure. [process of elimination]

[Oranga]

@kmrtnsn

Look at the amount of carbon in the “second stage” (I truly have no idea what to call it, the round narrow “waist” area in the bolt) There is a lot of carbon there, an unusually large amount. I am voting for a timing issue. There is too much gas moving to the bolt (over-pressure). Too small or crimped gas tube, too large a port hole in the barrel, something along these lines.

What are you using for a gas block? Gas tube? Carbine or 20" barrel?

I’m using a DD lo-pro gas block with a carbine length gas tube. The barrel is a 16" barrel from Del-Ton, I don’t know how big the port hole is supposed to be, but the one on mine is very small, much smaller than the corresponding hole in the gas block. I think the gas tube is correct as well, because it fits pretty much perfectly in the gas block. On the end that goes into the gas key, the last inch and a half is narrower though, probably to ensure clearance with the gas key, i don’t know if thats normal. But there are marks on it that suggest grinding down, and not crimping.

[kmrtnsn]

Can you post some picks of the bolt face and the BCG? Especially the front, top, and sides of the BCG? I know pics of the inside will be tough, but they would be nice to see, as would picks of the inside of the upper receiver.

Thomas, I get what you are saying but based on the amount of rounds he claims to have fired there is way too much carbon everywhere on the bolt, let alone in the area you and I are talking about. I imagine that the inside of the BCG is pretty scored up now.

[Thomas_M-4]

@Oranga

I’m using a DD lo-pro gas block with a carbine length gas tube. The barrel is a 16" barrel from Del-Ton, I don’t know how big the port hole is supposed to be, but the one on mine is very small, much smaller than the corresponding hole in the gas block. I think the gas tube is correct as well, because it fits pretty much perfectly in the gas block. On the end that goes into the gas key, the last inch and a half is narrower though, probably to ensure clearance with the gas key, i don’t know if thats normal. But there are marks on it that suggest grinding down, and not crimping.

Does the tip of the gas tube kinda mushroom shaped with a even wear around the widest part.
Also has the rifle short stroked with fresh rings in it?

[Thomas_M-4]

@kmrtnsn

Can you post some picks of the bolt face and the BCG? Especially the front, top, and sides of the BCG? I know pics of the inside will be tough, but they would be nice to see, as would picks of the inside of the upper receiver.

Thomas, I get what you are saying but based on the amount of rounds he claims to have fired there is way too much carbon everywhere on the bolt, let alone in the area you and I are talking about. I imagine that the inside of the BCG is pretty scored up now.

Just remembered if he had timing issues extraction to early there should be signs of it on the brass mangled rim or something to that point.
PMC is some dirty low pressure ammo it wouldnt take much to lay down carbon fowling.

[kmrtnsn]

Good points, Thomas. I need some more pics. I hope he can get them uploaded.

[Oranga]

Okay as requested, here are some pictures:

This is the best I could do to take a picture of the gas port.

Bolt face. I know there’s a lot of brass, it was from the Monarch ammo I was using.

This is the best I could do of the inside of the BCG. The chrome lining on the interior is actually all intact.

Some views of the outside of the carrier

Inside of the upper receiver

In this one, you can see where the gas vented around the “waist” of the bolt