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Posted: 8/24/2007 10:25:58 PM EDT
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I have a new front sight base (FSB) and the holes won't line up with the barrel for the taper pins. Is this common or a fluke? How should I handle this or do I need to order a new FSB? I took the rifle apart to install a free float tube, but I damaged the original FSB. I had a spare from a buddy and I just assumed that if would fit. Any help would be appeciated. Also - doese the gas tube need to be perfectly straight in from of the reciever? I can't get the barrel nut wholes to light up without being lose? Thanks Lovesbeer99 |
To answer the second question first---yes, the gas tube must be straight to go into the upper.. given the wide poundage variation allowed to install the barrel nut, I find it hard to believe that you can't line up the nut w/the hole in the upper within PSI limits; but I'm not there to see it.  Re the front sight base, I hate to say it, but you're basically screwed if you think you're going to replace it yourself. Each front sight base is individually matched to the barrel it is installed on, and you cannot take the base off one barrel, and mount it on another. You're going to have to get a new, undrilled base, and send the barrel and base out to one of several AR15 'smiths who have the equipment to properly mount the new base. |
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To expand on the barrel nut. The installation proceedure is to tighten it up snug. Back it off. and repeat this three times. This is to help spread the moly grease or anti-seize compound on the threads and to seat the threads. The barrel nut is then tightened to 35 ft/lbs with a torque wrench. Then the nut is turned to the next gas tube notch. Do not exceed 80 ft/lbs when tightening the nut. And as was already stated the front sight base is usually mounted to the barrel and the holes are drilled for the pins while it is on. This makes it almost impossible to find another base that will work on that barrel without matcing it as well, New FSBs are sold without holes drilled for this purpose. Another option is to get a folding front sight or a front sight base that attaches with set screws, or clamps on. Once the sight is sighted in use lock-tite to hold the screws in place. |
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