How to align clamp on FSB ?
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  1. #1
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    Default How to align clamp on FSB ?

    All-
    I finally have all the parts and am looking to get a service rifle build finished.

    Question- how do I get the FSB aligned to close enough to dial it in at range?

    I have:
    Flat top upper with Compass Lake Engineering A4 carry rear sight with the 1/4 MOA NM setup
    JP clamp on FSB
    18” barrel w/rifle length gas

    I might be regretting the FSB with set screws to work off barrel flats to dial in but wanted the adjustable gas on the JP.

    Bore sight?
    Jig up on flat surface and use a rail/indicator?

    Just get it close and hit the range?

    Thanks

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    I've done a couple by pulling the rear pin, pulling the bolt, mounting the open action in the bench vise with a bore sight out the window.

    Take a hard look through the sights to pick out a visible detail on the scene about 80 yards out, then find that detail or something close through the bore.....percussion adjust to match.

    In the black at 100 yds.....

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    Thanks


    ......

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    Start with the target at really close range, get the shots centered, then move target to a longer range and try again.

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    Shoot it. Adjust windage with the front base instead of the rear.

    --
    Pat Jones
    Firestone CO

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    In general, for AR sight block, I just line them up perpendicular to the barrel. I square up the barrel in a mill vise with a purpose built square plate and an adjustable parallel, but you can square it up with the flats on an upper and get decent results. On standard sights, there is a 3/8 in. counter bore for the sight post. Just use an edge finder and standard mill techniques to center the quill over the barrel. Then chuck up a 3/8 gauge pin in the quill and run it into the counterbore.





    Last edited by GenePoole; 05-10-2020 at 04:24 PM.

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    ^^^^^^^

    Thanks- Very sensible.
    For some reason when a person doesn’t do something all the time it seems like a mystery and you nail it- just treat like any other damn thing that has to indexed and centered on the mill.

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    I use a clamp on rear sight (Colt), set to mechanical wind zero and a GOOD collimator. AKA a bore sighting tool. Sweany Site-A-Line has never let me down. Can usually get to within 1 MOA at 200 yards.

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    Quote Originally Posted by kendog View Post
    I use a clamp on rear sight (Colt), set to mechanical wind zero and a GOOD collimator. AKA a bore sighting tool. Sweany Site-A-Line has never let me down. Can usually get to within 1 MOA at 200 yards.
    I am not familiar with that gear- will look into it.

    The rear I have is top notch- National Match clamp on built by Frank at Compass Lake Engineering.
    I would like to get out to service rifle matches at local club - I can chat the guys on the line up about gear when things open up again.

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    Quote Originally Posted by Trboatworks View Post
    I am not familiar with that gear- will look into it.

    The rear I have is top notch- National Match clamp on built by Frank at Compass Lake Engineering.
    I would like to get out to service rifle matches at local club - I can chat the guys on the line up about gear when things open up again.
    Site-A-Line, kits and accessories

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    Quote Originally Posted by Trboatworks View Post
    All-
    I finally have all the parts and am looking to get a service rifle build finished.

    Question- how do I get the FSB aligned to close enough to dial it in at range?

    I have:
    Flat top upper with Compass Lake Engineering A4 carry rear sight with the 1/4 MOA NM setup
    JP clamp on FSB
    18” barrel w/rifle length gas

    I might be regretting the FSB with set screws to work off barrel flats to dial in but wanted the adjustable gas on the JP.

    Bore sight?
    Jig up on flat surface and use a rail/indicator?

    Just get it close and hit the range?

    Thanks
    i think you might find the CLE barrel with flats will not play well with the JP front sight base. ?
    That said , alignment, get the gas ports lined up. Center the sight by eye and then you can set your no wind windage zero with the front sight base as long as you are with in the gas port alignment.
    IIRC the JP front sight base comes with provisions to pin the front sight once your happy with the placement/alignment.
    If your going to shoot service rifle theres little need for adjustable gas port.

  16. #12
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    Thanks- honestly I got lost in the woods of aftermarket ar parts.
    I bought A 18” fluted Faxon Heavy ‘match’ barrel w/rifle gas and the JP fits fine.
    I found the CLE and WA sources late in the game.
    If I had it to do again I would just pick up everything from CLE.

    I’m am now and have always been interested in just basic marksmanship.
    So much of the ar world is selling some version of tactical nonsense.

    I ended up with near enough to service rifle build to shoot matches given the more open CMP rules.


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