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Posted: 9/26/2004 1:39:28 PM EDT
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I’ve never seen a sighting in problem like this. Using a Bushmaster M4 A2 upper with vortex FS. It used to have the mini-Y and I had a vortex professionally installed. I couldn’t even get it in paper at 50 yards (I saw it kicking up dirt in the field) and at 10 yards it’s about 12” low. I tried ever possible windage and elevation setting I could possibly think of and it is still shooting extremely low. Right before that I was sighting in an Aimpoint™ on another M4 and had it zeroed after about 12 rounds. Any ideas of what could be wrong? Thanks… |
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Hmmm. Front sight post? Windage is a LEFT RIGHT not UP DOWN adjustment. Bring your front sight up. Test at 10 yards, 3 shots. Adjust, new target, 3shots. repeat I work on Elevation, THEN windage. Good luck. Sounds like your rifle has never been sighted in. Borrow a buddies BORE SIGHT It will get you on paper at least. |
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You dont make windage and elevation adjustments while sighting in for high/low POI issue. Also, this is strange... if this is the same barrel that came off the same upper receiver, then was reinstalled, and the POI changed that much.... sounds like something was not done correctly to me. You dial the A2 sight all the way down.... to the "3" or two clicks below the "3"..... in ancy case... just bottom it out all the way down. Then adjust the front sight post for correct POI height. To raise the POI you crew the front sight DOWN. It is possible you have a front sight made for a carry handle, which is taller than you need.... for an A2 sight. If you bottom out the front sight, and it is still hitting too low, then you need a short front sight post. Either swap them, or file yours (remove it from the FSB first!) to shorten it. If it is ridiculously low... and you would have to remove lots of metal from the FSB, take it to a gunsmith to have the barrel/receiver contact inspected. |
I was using an Aimpoint prior to vortex installation so I haven't really zeroed the irons like I should have lately. It might have been a little off but not like 3ft low at 50 yards. The Aimpoint is now on an A3 upper so I go to zero the irons on the M4 A2 with the new vortex and discovered the problem. I had a vortex installed on a post-ban 16" and the same time as the M4 mini-Y upper. I used them both on the same lower and the 16" is working fine so I don't think it is the vortex. Bore sighting my next step? Thanks… |
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Gunsmith informed me today that the bullet was striking the Vortex FS that was recently installed, causing it to be so far off sight. This was on the M4 upper. He also installed another Vortex on a standard 16" HBAR and it sighted in fine. Is there something about the M4 upper and vortex combo that would cause this problem? |
No. If you truly are striking the vortex.... one of two things: 1. The vortex is out of spec and bent or drilled/threaded imporpoerly.... simply changing out the Vortex is the fix. 2. The barrel was cut/threaded improperly, which is canting the Vortex FS. Both are possible, but pretty uncommon. If it truly is striking the vortex, the groups would not only be way off, they would be ALL OVER the place, as there is nothing consistent about striking something that close to the muzzle. Can you see the hit marks? The copper should be pretty visible, I would think. |
Shot groups were consistent, about 12" low at 10yds and 3ft low at 50yds but both surprisingly held a very tight group. Both FS were brand new vortexes. Hopefully I can get the upper back sometime next week as well as the exact reason for this problem. Thanks. |
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