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Posted: 4/2/2011 11:36:14 AM EDT
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I just completed another build. I have built about 15 or so ARs for myself and friends so this is not my first rodeo.
Went to test fire it today and it is a single shot rifle. It chambers rounds easily, it fires the first shot but the bolt will not move to the rear. Pulling the charging handle allows another round to be chambered and fired. The movement of the bolt to the rear with the charging handle is smooth and easy. I suspect a gas issue; I assembled the upper from scratch. The parts include 20” DPMS upper, standard FSB, and a new gas tube. After I assembled these components, I blew through the gas tube to check for proper flow and any obstructions. I can rule out the ammo. It is factory loaded surplus that fired without issues in my other AR today. I’m going to pull it back apart to check it again, I just wanted to throw it out here to see what all you smart AR guys think. Thanks Vic |
| Since you have air flow through the GB to the tube (although it still could be slightly misaligned restricting the gas flow some) I would guess the gas key on the carrier is leaking due to a loose/broken screw(s) or that it is not mated/lapped/sealed to the carrier properly ... do you have another BCG you could try? |
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Quoted:
Figured it out..when pinned in, the FSB was mis aligned. Guess I'm looking for a FSB at tthe gun show next weekend. Thanks Vic I doubt there is anything wrong with the sight itself. There was another member here some time back that had a canted FSB and it turned out to be bent taper pins ... he replaced the pins and the FSB straightened right up. If that isn't the problem and the holes are drilled canted then a new pinned sight isn't going to help and you might have to go with a clamp on FSB version so proper port alignment can be achieved. 
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Figured it out..when pinned in, the FSB was mis aligned. Guess I'm looking for a FSB at tthe gun show next weekend.
FSB are specific to each barrel and are not interchangeable. After the FSB is installed on the barrel the taper pin holes are drilled in a fixture and pins installed. |
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Quoted:
Figured it out..when pinned in, the FSB was mis aligned. Guess I'm looking for a FSB at tthe gun show next weekend.
FSB are specific to each barrel and are not interchangeable. After the FSB is installed on the barrel the taper pin holes are drilled in a fixture and pins installed. This would explain a lot. When the pins are installed, the FSB is too far fwd for the gas holes to align. The triangle cap has abou1/8 - 1/4 free play. The holes are just off enough to make re drilling impossible. A friend has a FSB I can try. If this one does not line up, I guess I am going the clamp on route. I was hoping to keep it "A2" looking. Does anyone one know of a clamp on A2 style front sight? |
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Thanks..looks like just what I need. |
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