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Thread: My AR is shooting 20moa right

  1. #1
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    My AR is shooting 20moa right

    Hey,

    My AR is shooting 20moa right at 25yds.

    I have a micrometer, is there a way to look for sight cant of the FSB?

    Barrel is new. There are no hurricanes here.

  2. #2
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    a canted FSB wouldn't cause a 20MOA... if you can't get POI within 20" of POA then you might have a FSB issue, but you'd be able to see a cant like that.

    what do you mean by MOA? extreme spread? 5 or 10 shot groups with holes 5" apart at 25m?

    what kind of barrel and ammo?

    ETA: totally didn't read the original post right... i see now you said shooting 20MOA to the right

    what's the weapon? what sights you got on it? does the FSB LOOK canted? what kind of barrel/muzzle device? check for damaged crown/burrs on the crown?
    Last edited by bkb0000; 03-29-09 at 04:01.

  3. #3
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    I gotta ask do you know how to adjust the sights?

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    20MOA to the right.

    The group sizes are about 3-4MOA.

    This is with Hornady FMJBT "training" 55gr .223 steel case. Laqured, which is why I don't shoot rapid fire with it.

    16" midlength 1:9 armalite barrel. Just had the FSB swapped for an F-marked by ADCO. Standard irons and flat top carry handle. A2 FH. No apparent crown damage.

    I don't use rods or brushes, I use boresnakes and weed-wacker line with patches on it.

    EDIT: Yes. Turn the rear sight drum to the bottom. Center both the front post level with the "shelf" and windage on the rear. Turn up to the "Z" mark. At 25yds at the 6/3 mark any adjustment for elevation is done with the front post and windage is self-explanatory.

    EDIT2: I tried some UMC .223 55gr and it did the same thing. I have some M855 and M193 but that can wait. I already know it can do 3moa on M193 without too much difficulty and M855 is easy 4moa. This is all done prone with a loop sling -- I don't use benches.

    EDIT3: it does not look canted. I experimented with cant on my 10/22 a while back and you have to get some 20º of cant before things look dirty. I have not had a single FTF or FTE with this carbine, I did have a IMI .223 55gr (shoots 3moa at 300yds...good stuff) that had a damaged shoulder that stovepiped, aside from that nothing. At least 120 rounds have gone down the barrel now.

    Shot 2moa with a M261 GI .22 bolt kit too. I oughta get one of those things.
    Last edited by 298436; 03-29-09 at 04:25.

  5. #5
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    so you obviously have windage shoved up against the housing and still not zerod, right?

    if your windage is all the way over and you're still 20" off, if it's the FSB you'll be able to see the cant. wouldn't be the first time ADCO put on a crooked FSB- they do so many its bound to happen from time to time. but unless it's visible, i think there's something else going on.

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    Well I counted the clicks back from zero (as in, centered on the windage graduations) and it's ~20 clicks over. I have half-minute clicks if I recall right, they could be 1moa clicks -- right now I'm to concerned with the 20moa right to run a "box" -- 10 clicks up, fire a group, 10 clicks right, fire a group, 10 clicks down, fire a group, 10 clicks left and fire a group.

    I do need to know how much MOA do I get per click on mine, from a table it's about 1.75MOA for the front and 3/4 for the rear or something like that. A box will tell exactly what it is.

    With the windage cranked over, it shoot fine. But no rifle should be cranked that far over except an Indian or Chinese AK47-copy-reject.

    It cycles and locks back the bolt fine, so I know the gas port is lined up. If the original FSB shot the same way but not cranked so far over, then why would the F-marked swap be so far over and still cycle?

    It has to be something. I put on a post on the ADCO section of ARFcom and see what they say.

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    If its a rail mounted sight loctite them down. Also zero the elevation first and when thats on then zero the windage. Then fine tune.

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    Quote Originally Posted by Shihan View Post
    If its a rail mounted sight loctite them down. Also zero the elevation first and when thats on then zero the windage. Then fine tune.
    Thanks, aye on the ele/windy thing. Elevation was fine.

    It is a standard F-marked FSB, I have no rails except an MI FSB light mount. And that was already ruled out since it shot the same with it or without it.

    Sling pressure was found to do nothing immediantely conclusive. And then sling pressure doesn't cause windage stress.

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    Just a Thought

    The only similar story that I had any involvement with had a bend in the barrell. It was barely noticeable until we took the handguards of the rifle.
    K.I.S.S. (Keep it Simple Stupid)
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  10. #10
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    So what shall I do next?

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