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Posted: 3/3/2008 11:28:16 AM EDT
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I didn't find the answer on any FAQ's, so here goes: I tried sighting in my new gun at 25 meters. The red dot Aimpoint was golden; well within MOA consistently with only minor adjustments. (The most accurate M4/AR-15 I have shot.) The Midwest Indistries folding front and rear sights were more difficult. The sights resulted in tight groups but well to the right and low. I adjusted both elevation (front flip-up) and windage (rear flip-up), which resulted in acceptable improvement with elevation but windage was still way off. (The MI rear flip-up sight does not have any elevation adjustment; windage only.) The rear sight was adjusted very far to the left, and was still not causing the POI to move suffieciently towards the middle. I tried different ammo with little or no improvement. (PMC 55 grn, Winchester 55 grn, Lake City 62 grn, Federal 64 grn.) The gun specs are: CMMG flattop, 16" medcon bbl, 1:7 twist, MI FF rails. I know the 1:7 bbl can handle (needs) higher grain ammo for maximum accuracy. However, it seems unlikely that 55-64 grain ammo could perform so poorly at such short ranges. Also, wouldn't "tumbling" bullets not produce the tight groups? Given the Aimpoint's success, I have ruled out any barrel issues. Also, I just don't think my sight picture is to blame; I have about 20 years experience with firearms. There was a strong rear/left-to-right cross wind but at only 25 meters, I can't believe it was that much of a factor. I'm ready for input! Thanks for helping. Big B in Norcal |
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If you have the flip up front, what is the sight attached to? Really, lets just cut to the chase. Start off with confirming that the center bottom section between the barrel extension feed ramps is center on the upper receiver front take down lug. If the barrel is indexed on the upper correctly (barrel lugs aligned so the bolt will enter/exit correctly), then the barrel is indexed to the upper correctly. Now lets more onto the front sight block, or float tube if that is what you have the front post attached to. Zero out the rear sight, then while laser'g down the bore, adjust the front sight attachment "thing" to the center out the front sights on the laser point (read if you are just laser'g a few yards out, then the sight line will be a tad high over the bore sighting point/dot). Note: if you have a gas block, then it retains on the barrel via allen screws. If you have a float tube with a front sight attachment block, then you will need to loosen up the float tube, and reindex the tube system so the front sight is bore line centered. P.S. Welcome to the site!!! |
Simple, your going to need to re-index/reinstall the FF to cant/index the front sight correctly with the center line of the upper receiver (rear sight centered at sight in). |
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