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Posted: 11/25/2003 10:14:26 PM EDT
Hey all. Got an A2 upper where everytime I cycle the action, the elevation knob keeps turning clockwise. I haven't fired it yet, but I expect the same thing to happen, even worse with the recoil. Is there some way I can tighten this down so it doesn't move around so easily?
Link Posted: 11/25/2003 10:44:38 PM EDT
How large is the gap between the front of the rear sight base and the rear of the upper receiver? If you run the rear sight base up (in elevation) does the gap close? With the rear sight all the way up is the thread on the front or on the back of the shaft highest?
Link Posted: 11/25/2003 10:44:39 PM EDT
Link Posted: 11/26/2003 12:38:27 AM EDT
How large is the gap between the front of the rear sight base and the rear of the upper receiver? If you run the rear sight base up (in elevation) does the gap close? With the rear sight all the way up is the thread on the front or on the back of the shaft highest?
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Not sure exactly what you're asking. At 3/8, the sights are completely down, touching the receiver.
Chances are good that it's missing the detent ball and/or spring under the elevation knob. Does it click when you adjust elevation, or does it spin freely? The A2 rear sight has a lot of small parts that all need to go together perfectly for it to work right. I've seen ones improperly installed before, and missing parts.
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The sights do click for adjustment, so I don't think a detent is missing, maybe a weak spring?
Link Posted: 11/26/2003 2:30:35 AM EDT
Originally Posted By FNMI_Rifleman: Not sure exactly what you're asking. At 3/8, the sights are completely down, touching the receiver.
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I was asking about the gap between the front of the rear sight base (the edge that holds the spring and detent) and the rear of the upper receiver where the detent touches it. How wide is that gap? [img]http://photos.ar15.com/WS_Content/ImageGallery/Attachments/DownloadAttach.asp?sAccountUnq=12467&iGalleryUnq=1145&iImageUnq=20153[/img] The gap I'm speaking of is forward of the "UP" on the rear sight base. Does it get smaller as you rotate the elevation wheel? With the rear sight base fully elevated you can see the threaded shaft that supports it. Is the thread on the front of the shaft higher than the thread on the rear of the shaft?
Link Posted: 11/26/2003 1:19:46 PM EDT
In the down position, the gap is about maybe half a millimeter, and gets smaller as I rotated the sight up. The threads on the shaft are higher toward the front of the receiver than they are towards the rear.
Link Posted: 11/26/2003 7:58:18 PM EDT
[Last Edit: 11/27/2003 4:00:52 AM EDT by Dano523]
Just a thought, you are aware that the windage knob/wheel is a two-piece design. The bottom-knurled section is the inner piece, with the Numbered upper section the outer piece. With the dial set to 3/8 use a Allen wrench and go in the hole just in front of the aperture (peeps) on top of the sight housing and tighten the outer ring Allen screw.
Link Posted: 11/27/2003 7:31:48 PM EDT
Originally Posted By FNMI_Rifleman: The threads on the shaft are higher toward the front of the receiver than they are towards the rear.
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The thread on the rear of the shaft should be highest. This is what pushes the RSB forward against the spring and detent when the RSB is fully down. As the RSB moves up the rear thread[b]s[/s] counteract the spring pressure. That is why the gap closes as the RSB moves up.
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