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Thread: How to install A2 front sight?

  1. #1
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    How to install A2 front sight?

    My father wants to install a A2 front sight to replace the gas block he already has. do I just need a sight and taper pins?

    this is on a M&P AR15OR. search didnt provide much help.

  2. #2
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    You cant install a FSB on a barrel that isn't drilled and has the cut outs for one.
    But what then is capital punishment but the most premeditated of murders, to which no criminal's deed, however calculated it may be, can be compared? - Albert Camus

  3. #3
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    Your best bet is to send it to Adco.

    The old block must be removed, a new unused A2 sight supplied.
    The sight block is then placed on the barrel in a jig, drilled through the sight and barrel at the same time. Then reamed, then pinned.

    You may be better off getting a different rifle or upper.
    Last edited by An Undocumented Worker; 12-24-11 at 22:37.

  4. #4
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    As other have stated you are going to have to have the gas block removed, a new FSB pinned into place, etc...

    It's not worth the cost. Sell the current upper and get a good one or deal with what you have.

    Quote Originally Posted by LWatson View Post
    My father wants to install a A2 front sight to replace the gas block he already has. do I just need a sight and taper pins?

    this is on a M&P AR15OR. search didnt provide much help.





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  5. #5
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    Quote Originally Posted by Iraqgunz View Post
    Sell the current upper and get a good one or deal with what you have.
    Agreed. If you have it installed and they job gets done poorly. You'll just end up with a big waste of money.
    "You people have too much time on your hands." - scottryan

  6. #6
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    FWIW...

    I'm not saying what I did is 'proper', nor accepted. It just happened to work for me.

    In a nutshell - I got a barrel assembly through a friend in the industry (the company shall remain nameless) and when I got it, several months later, it came with the wrong FSB - it was shaved down, when I asked for a "standard" one. Rather than dealing with the immense delays that I've already experienced, I decided that since I'm pretty much stuck with the barrel, that I should try to 'fix' it myself. I know, never a good idea.

    Anyhow, with parts ordered through BCM and Brownell's, i decided to take the barrel apart, and install a new, non-drilled FSB onto a barrel that has already been drilled and pinned for a FSB.

    I realized that the holes need to align 'exactly', so what i did was take a few properly sized drill bits and pass them through the sling mount hole, as well as the gas tube roll pin hole to get the more or less aligned.

    I placed this in a vise, and with a cordless drill and the proper bit, marked the holes, drilling through the old FSB, into the new. Then, for whatever reason, i decided that I am going to put this in a clamp, between two pieces of wood / plywood and and using a drill press, drill through one side of the FSB. I did this thinking that I probably won't be able to go through both sides, since there's no barrel to support the drill bit once it goes through one side... and sure enough, it did deflect.

    at this point, i thought since one side is drilled, i can see if the holes line up (which it did, more or less) and using BRDE's FSB fixture, drill the rest of the way through.

    Yes, it was a major PITA, but despite the minor misalignment issues I've had, i was able to compensate elsewhere, and was able to install a new FSB onto an existing barrel. Sorry, I have no pics to share because I was just not in the mood - but i do have a pic of the completed rifle... if i can figure out how to post it.

    And for those who are considering doing this, I am not taking any responsibility for messed up FSB or barrels or for that matter, anything else that gets messed up. Just wanted to share that it is possible. and yes, the rifle functions - even with a home brew nickle plated BCG. I did use a no frills drill press, one cordless drill and the BRDE fixture. And some common sense.

    Again, for informational purposes only.

    rd

  7. #7
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    rubber ducky, did you finish the holes with a taper pin reamer?
    Oh no, not another lube thread! Read this first: Lubrication 101.

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    yes, sorry - i didn't include that, but i did. I used the brownell's one with the handle, but it took me forever and a half to ream it, so I dremeled the handle to i can chuck it in my cordless. that made it a lot easier... but i can see this easily over-reaming if you're not careful...

    btw, it was my very first attempt at installing a FSB. I've never done one previous. But I can see why this is avoided... you can easily ruin one or both components.

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    And if the gas block you have now has a rail. You can always buy a LMT buis and slap on there , Just a thought

  10. #10
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    Quote Originally Posted by motorolahamm View Post
    And if the gas block you have now has a rail. You can always buy a LMT buis and slap on there , Just a thought
    I don't think the LMT front buis is the correct height for a gasblock rail, but rather for a railed HG at the same height as the receiver rail.
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