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Thread: re-pinning front sight base?

  1. #1
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    re-pinning front sight base?

    I have a surplus M16A2 upper that has a wobbly front sight base. It looks like the pins aren't pressed in all the way. Can I tighten the front sight base by removing the pins, and pressing new pins in?

  2. #2
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    Why not knock the pins in all the way? I doubt the existing pins have deformed so replacing them will not solve the problem.
    B.A.S. Mechanical Engineering Technology

  3. #3
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    If the pins are installed and removed repeatedly, would they lose their shape?

    Would removing the old pins, reaming the holes and installing new pins hurt anything?

  4. #4
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    They might start to mushroom a bit but the taper should be intact.

    From a machinist's standpoint, you could ream the holes and install new pins, you would just have to ream slighty deeper and the new pins would be recessed a bit further. You'd have to make the judgement on reaming depth but I wouldn't want the head of the fatter side to be below the face of the fsb.

    The main challenge when reaming for taper pins is keeping the fsb aligned with the gas hole: There's fixturing to do this. At any rate it would be a task I recommend you entrust to somewhere like ADCO

    Quote Originally Posted by bingeebob View Post
    If the pins are installed and removed repeatedly, would they lose their shape?

    Would removing the old pins, reaming the holes and installing new pins hurt anything?
    Last edited by Eric D.; 02-15-11 at 13:16.
    B.A.S. Mechanical Engineering Technology

  5. #5
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    If the pins are messed up buy new Colt or BCM pins and install them. If their CMMG pins they're WAY too soft anyway. I hate those CMMG pins.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

  6. #6
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    So I slid the pins out with just my fingers... they appear to be straight (they roll straight on a hard surface) and the holes in the FSB are not noticeably tapered.

    If I buy a Brownells front sight base block, new Colt pins, and a reamer, gently ream the holes then pound in the new pins, will I be doing it right?

  7. #7
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    Ideally, you ream one hole with the othernstill securely pinned to ensure constant proper alignment, punch in new taper pin and ream the remaining hole. Since your pins are loose to begin with, i suggest finding a way to secure both the barrel and the fsb. Ive never used the brownells bench block before but I suppose keeping it flat on the bench and securing the barrel would do the trick.
    Edit:
    Sorry, I re-read your post and saw youre still looking to purchasethe FSB bench block. Id hold off doing so and wait for more responses. Others may have better, tried and tested methods of securing the barrel and FSB for reaming.
    Last edited by Col_Crocs; 02-18-11 at 19:08.

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