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Posted: 3/15/2011 7:13:48 AM EDT
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13 month old XM15-E2S (about 1.2K rounds) has been having issues for some time short stroking and failure to feed. Bolt will no longer stay open on last shot. I found this last night and looks like a broken gas ring are there any secrets to replacing these?
http://i1199.photobucket.com/albums/aa480/Boresighter1/e7bf5110.jpg I then decided to dig a little deeper. This this normal carbon build up or do I have a gas leak? http://i1199.photobucket.com/albums/aa480/Boresighter1/698f2807.jpg |
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The AR should be able to function with a single gas ring. However if one is damaged it is likely the others are worn or damaged as well. Gas rings are a cheap and easy fix. Simply use a thumb tack or similar pointy device, to get underneath the ring and lift it out. If you replace one you should replace all three.
With the bolt carrier assembled, extend the bolt, place the face of the bolt on a horizontal surface. Good gas rings should be able to hold the weight of the carrier. If the carrier slides down over the bolt then your rings are bad. |
| Replace the gas rings and try again. Check for any burrs inside the carrier where the bolt goes. Gas rings don't normally just break like that. Check your gas key for tightness. Do not mess with you gas tube right now. The carbon build up is normal and helps seal the gas block area. What ammo are you using? |
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On the gas rings, starting with the one closest to the back end of the bolt, use your finger nail to lift one edge of the ring out of the channel, then ride the rest of the ring out the side. now so the second and the third as well.
Now when you go to install the new rings, remember that they are stamped produce, with the bottom having a sharp edges, and the tops a more round edge. Install the rings one at a time like you took them off, and the sharp edge side of the rings should be faced towards the back of the bolt. Also, Do not try to spread the rings open to far or you will snap them. Just get a edge point at the slit into the bolt channel, then ride the ring with your thumb nail the rest of the way around to allow it to snap into the channel as well. |
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Thank you for the help so far. I put new gas rings in tonight. They seem tight as it takes a bit of effort to move the bolt in and out. Loaded 2 rounds (UMC factory) both fired (an improvement) but the bolt did not stay open on the second shot.
Changed mags (with new lot UMC) and same issue. Tried American eagle and the bold held open. But what gets me is that this thing has had a steady diet of UMC without issue for the first 900 rounds. Gas key is tight, no burrs inside BC, bolt is wet. I think I am back to a gas leak at the gas block. Any advice? |
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Yes the gas rings should cause a bit of difficulty when inserting the bolt into the carrier. You should spin the bolt slightly as you push it in.
Double check the gas rings again make sure they did not suffer any damage on the first shot. Can you give a photo of your gas tube inside the upper. It is possible the gas tube is worn and not getting a good seal when it is inside the gas key. Replacing the gas tube is a cheap easy fix also. Premature wear can occur on the gas tube if it is not indexed properly or bent slightly. The photo of the gas tube at the gas block is a bit shadowy to me, but if you suspect things dont look right there I would be interested to see the condition of the tube that is hidden in the gas block. Was this a built rifle, used or new from the manufacturer? |
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The bolt holding open after your last shot doesn't have anything do do with gas rings, if I'm not mistaken.
Remove your rear take-down pin, hinge the rifle open at the front take down pin, and insert an empty mag into the magazine well. You should see the follower of the magazine pushing up on the bold catch, making the bolt lock back on an empty mag. It sounds like your mag springs don't have enough oomph to push the bolt stop up, or maybe the little tab broke off your bolt catch, so now there's nothing for the magazine follower to interact with..? ETA: After re-reading some of your posts, maybe it is a gas-related issue. It's possible that you have a leak and that's preventing the action from cycling fully, which would prevent the bolt catch from stopping the bolt. |
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I removed the gas tube and cleaned (outside) the ends. The top of the tube that enters the kas key was really fouled. Then cleaned the inside of the gas block hole with solvent followed by brake cleaner and then compressed air. Bunch of carbon flushed into the barrel so I ran a few swabs down. Limited testing in the backyard indicates problem solved. Maybe this UMC stuff is really dirty? Funny as I don't even find it accurate or cheap. I will run a few mags of different ammo through it this weekend and report back...
Thanks for everyones help!!!! |
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