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Posted: 4/28/2008 12:18:10 PM EDT
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I recently assembled an AR-15 with a Gov't profile barrel 1:7 twist. I installed a CMP match front post sight (the one with the slant on it) and put in a NM site base 64 threads/inch and a NM windage knob. Went to sight in over the weekend and the rifle shoots high and to the right 7" over (R) and 6" up. This is with the site base as low as it will go? I adjusted the front post but the NM post has to move in complete turns. Any suggestions from people that have had built there own rifle (match) and had these problems. I have considered putting an adjustable front site base which will solve the windage problem, but that won't solve the elevation problems with the NM rear site base. |
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Adjust the FSB to zero out the windage (read use the set screws), then pull the FSB and shorten the post to correct the elevation problem. Note: your rear sight zero should be about three clicks up on the elevation for your 200 yard zero (100 if you are having to shoot reduced ranges/targets). Also, since we are talking CMP, mark the elevation knob for 200,300, and 600 yard zeros. On the windage knob, mark it for a 200 yard dead calm zero. These settings/marks will get you in the hunt, but you will still need to go after the knobs for fine tuning per conditions. If you are not using an adjustable FSB, then a leather mallet will resolve the windage problem (used to slip the entire barrel in the upper socket via holding only the upper receiver and striking the FSB just above the barrel to slip it in the upper barrel socket). FSB post drill spun using a file will shorten the it, and keep the top square. Also, while you have the post in the drill, straighten the post is needed. |
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