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Posted: 6/7/2010 4:33:29 PM EDT
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Zeroed my new M16A4 clone this evening. Shoots great, feels wonderful. One hang-up, though... I needed to bring the front post a LOT. I kept the rear bottomed at 6/3. The top of the post is above the ears of the front sight. If I recall, this is not an uncommon problem, but I cannot remember what to do with the rear sight to fix it. HALP PLZ!
Edit to fix. |
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Quoted:
What distance did you zero at? Do you have a F marked FSB? What brand is your carry handle (is it a bushmaster?) An A4 should have a 6/3 carry handle, the A2 should have a 8/3 carry handle sight. fixed it for ya OP: you said you "need to bring the front sight post a lot." I assume you mean bring it up. Do you need to bring it up more than it will allow? If so, the easiest fix is to get a taller front sight post: found here |
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Worse comes to worse, I'll play with the elevations on both front and rear and find something that works, but I remember reading somewhere about an easy fix about bringing one sight up and one sight down. Anyone recall this, or am I just crazy? see my post above |
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shouldn't a rifle use an 8/3 elevation knob and a carbine use a 6/3? Fixed carry handle uppers use 8/3 Detachable carry handles use 6/3. There is not enough space on the detachable carry handle to use the longer cam of the 8/3 adjuster. To the OP, do you have a quality carry handle? There are 2 heights of carry handle. Milspec height, and bushmaster height. The bushmaster carry handles are shorter and ment to be used with non- F marked carry handles. The lower carry handle could throw your impacts high. Oh and its 36 YARDS for a 300M zero on 6/3. You could use 25 METERS and 6/3 + 2 (z mark) |
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Worse comes to worse, I'll play with the elevations on both front and rear and find something that works, but I remember reading somewhere about an easy fix about bringing one sight up and one sight down. Anyone recall this, or am I just crazy? see my post above Thanks, but I think that I figured it out... My buddy was fiddling with the rifle before I zeroed it, and may have played with the sight, not knowing I wanted it bottomed out. I looked at it just now, and it was not bottomed, so this is almost certainly what happened. I shall use that as a back-up, but will head back to the range soon to try again making sure that the rear sight is bottomed. Thanks for the help, guys! |
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Quoted:
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shouldn't a rifle use an 8/3 elevation knob and a carbine use a 6/3? Fixed carry handle uppers use 8/3 Detachable carry handles use 6/3. There is not enough space on the detachable carry handle to use the longer cam of the 8/3 adjuster. To the OP, do you have a quality carry handle? There are 2 heights of carry handle. Milspec height, and bushmaster height. The bushmaster carry handles are shorter and ment to be used with non- F marked carry handles. The lower carry handle could throw your impacts high. Oh and its 36 YARDS for a 300M zero on 6/3. You could use 25 METERS and 6/3 + 2 (z mark) The handle is a BCM, as is the rest of the upper, save the compensator. This was a BS estimated 36ish meters anyway... I suppose this was less of a zero and more of a "shoot her and get her on paper." I will most likely be able to get to a 25yard range before I get back to this one, anyway, so it will be properly zeroed soon. |
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I have the same issue with my 20" (w/"F" marked FSB) A4 upper. I have the rear bottomed out, the front raised so it is just above the front sight "ears" and I still need to come down another inch or so to be zeroed correctly. Everything is mil-spec from a top end manufacturer. Do the military A4s have this issue or do you just not hear about it because everybody uses optics now?
It got me so frustrated that I took that upper off, put it back in the box, and put a 16" middy on this the lower instead! I haven't fired the middy yet, but hopefully I don't have a similar zeroing issue with this upper. |
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Go back and use the 25 meter and go 6/3 + 2 up. That will put you on at 300, or leave it at +2 and it will bee good for shorter ranges ie. inside 50/75.
That is what I have done and seems to work out ok. Just my opinion anyway. When I get my eotech, I will sight it in at 50 yds. and just use hold off for diff. distances. 
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Quoted:
Quoted:
What distance did you zero at? Do you have a F marked FSB? What brand is your carry handle (is it a bushmaster?) An A4 should have a 6/3 carry handle, the A2 should have a 8/3 carry handle sight. fixed it for ya OP: you said you "need to bring the front sight post a lot." I assume you mean bring it up. Do you need to bring it up more than it will allow? If so, the easiest fix is to get a taller front sight post: found here You would never settle on a solution that leaves the sight post extending up above the ears. Fortunately he has found the problem - the rear sight had been monkeyed-with and he didn't check it before firing. Rather bad form, that, old bean. |
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Here is my recommendation:
Go look up the RIBZ. Bottom out the carry handle at 6/3 You take a small allen wrench and insert it into the hole right infront of the rear aperture. Using about 3 (THREE) turns, loosen that allen screw (DO NOT REMOVE) Turn the bottom part of the elevation knob to raise the rear sight 6 (SIX) clicks. Tighten allen screw. Zero as per my instructions above 36 YARDS on 6/3 -or- 25 METERS on 6/3 + 2 (z) Then 6/3-4 should be a 200m zero (8/3-2 is very close on the A2, 6/3-4 is a little off, but close enough for Govt work) 6/3-6 (bottom out) will be about a 100m zero. (not dead on, but close) 
The main benefit is more options with your rear sight. This will also raise your rear sight requiring moving the line of sight down for the BZO. This may help with your front sight elevation problems. (did I word that right? Am tired right now) Edit: Just saw that you figured out your problem. Well I still recommend the rear sight alteration I just posted. |
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