FTE after new (used) upper was installed

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[ARCHIVED THREAD] - FTE after new (used) upper was installed

Posted: 2/26/2006 6:26:08 AM EDT

I changed uppers and now it will not eject. It will pick the round up, chamber it but once it's fired I have to cycle the bolt manually. Then it picks up the next round and so on. Any ideas what might be causing this ?

Posted: 2/26/2006 11:35:45 AM EDT

[#1]

What type upper (read need full details such as a FSB or gas block, new B/C or old one being used, and so on)?

Posted: 2/27/2006 6:15:16 AM EDT

[#2]

It's a FSB and I'm using the same bolt as I was before. But I think I may have found the problem. For some reason the gas tube pin is missing. Now wouldn't that cause the gas to exit out of the gas tube pin hole instead of working the bolt back ?

Posted: 2/27/2006 10:40:44 PM EDT

[#3]

Since the end of the gas tube is end pluged where the pin goes threw, the leak should be minimal, but the real question is if the gas tube is installed correctly, or the FSB/gas tube ports out of alignment (read blocking each other)?

Posted: 2/28/2006 2:40:37 PM EDT

[#4]

I'll check on that. Thanks for the help.

Posted: 3/4/2006 8:27:23 AM EDT

[#5]

Okay I checked the gas tube and FSB. Even hosed them down with gun scrubber and blew them out with air. Still doing the same damn thing. Any more suggestions ?

Posted: 3/4/2006 12:05:06 PM EDT

[#6]

I'd say that installing a new roll pin will cure the problem. If it is missing, the gas tube can rotate in the FSB, or even move in or out. All of this can cause misalignment and gas loss.

You can try to find a new roll pin locally. It needs to be 0.312" (5/16") in length with a diameter of 0.081". As a test, you might use a small nail to temporarily pin it in place to see if the rifle will function correctly.

[ARCHIVED THREAD] - FTE after new (used) upper was installed

AR-15 » Troubleshooting

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