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Posted: 11/24/2007 6:18:15 AM EDT
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I just got a stripped upper/barrel combination that appears to be in excellent condition. There are marks on the FSB that indicate that it may have been used to hold the barrel when the receiver was torqued down. Using a straight edge down along side the carry handle (A2), the FSB seems to be canted to the right about an 1/8 of an inch. I have not got the rear sight assembly in yet to sight it in. If it is canted, how do I fix it? It has the taper pins and is on extremely tight. Thanks Dewayne |
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It is prob not the FSB that is canted, but rather the barrel is not on straight with the upper. It is an easy fix if you have the tools. When the barrel extension is put in the upper there is an index pin, that keeps the FSB pretty much centered, but while you tourqe the barrel nut on, it can shift the whole barrel and the FSB will apear canted. You can also remove the taper pins, and center the FSB and drill new holes, but this is not the ideal fix. |
Take a look at the center of the feed ramps against the center of the front bottom lug. Is the center of the ramps centered on the lug? Next try the B/C in the upper and confirm that the bolt lugs will enter and exit the barrel extension lugs without binding. If the two items above are doable, then the barrel can be re-indexed at the range via a leather mallet to adjust the front sight (slip the barrel in the upper receiver) to allow the rifle to be zeroed with the rear sight dead center. Note: if the barrel extension is dead center and the FSB is still canted (read rear sight pegged to one side to zero the rifle) then chances are the barrel was not assembled correctly, hence the FSB was not indexed on the same barrel plain as the barrel extension pin. There is a solution for this that is on the inexpensive side, but will take more that a leather mallet to correct. |
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Thanks Dano523. I am very new to building AR-15's and will check the lugs in the morning. I took the FSB off tonight when I got back from the range. The gas tube and port looked ok to me. My bolt and carrier are also new, but seem to lock up fairly easy. I have another Ar that has never malfunctioned. I will take it to the range and maybe swap out a few parts and see what happens. The lower I was using today did seem to have a stronger buffer spring than my other AR. Thanks again Dewayne |
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