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Thread: S&W M&P15/Stag front sight post height

  1. #1
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    S&W M&P15/Stag front sight post height

    I know this topic has been posted before for Stag uppers, but I've got a S&W M&P15 (made by Stag) with the same problem, and I was curious if there are any M&P15 owners here who have contacted S&W about this and what their response was. I'll probably call them on Monday, but would like as much info from other owners as possible beforehand.

    Again, this problem involves having to set the front sight post so high that the top of the post sticks up above the level of the protective "ears" of the FSB when attempting to zero the elevation of the M4 carbine. This problem seems to be isolated to owners of Stags and S&W's. A friend of mine who owns a Bushmaster M4 type does not have this problem. Several people have mentioned having this problem when using the ARMS#40 backup rear sight(including me), but I reinstalled the original carry handle rear sight and am having the same problem with that, so it doesn't appear to be a sight problem.

    Some people, including me, also have a problem with having to move the rear sight aperture way to the right in order to zero the windage on these rifles.

    There is also a discussion about this problem in another forum:

    http://www.ar15.com/forums/topic.html?b=3&f=18&t=311257

  2. #2
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    If you don't have a F stamped front sight base, then your front sight post will look like it's going to fall out. Bushmaster sells a .030" taller front sight post for $5.50 that will cure this.

    Here's some pics I found on another website showing the difference of a F FSB and a standard one.


    Chief Armorer for Elite Shooting Sports in Manassas VA
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  3. #3
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    My S&W has an F marked on the side.

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    http://www.bushmaster.com/shopping/scopes/9349056-m.asp

    This is what I used on my flat top upper without the "F" front sight base. Without this I had the same issue that you described above. Quick and easy fix and this is a well documented issue with flat top receivers and carry handles.
    Back in the land of Waffle House and sweet tea!!!

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    Interesting that we are seeing this come up a lot now. I wonder if a batch of A2 FSB's got mis-marked??

    As long as your windage isn't more than 11 clicks either way, I think your fine.



    C4

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    I just measured my S&W front sight base. It is marked with the F and matches the measurements shown above for an F base. While I don't know when it was made I traded for it new in the box back in November. Perhaps this is a recent problem?

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    My front sight base is marked with the "F". I did order the taller front sight post from Bushmaster and installed it, but the problem with it and the original is that the top of the post sticks up above the level of the protective "ears" of the FSB and is therefore exposed to possible damage if I drop it or bang it against something. This defeats the purpose of the protective "ears". I tend to agree with others who say that there is a manufacturing flaw with these uppers made by Stag, probably with a limited batch. If they are mil spec, I don't think they should be this way. A friend with a Bushmaster M4 and the ARMS #40 rear sight does not have this problem. His front sight post is well below the top of the protective "ears".

    Here's my S&W front sight:



    And my Colt front sight:



    I believe that the top of the front sight post should be sitting about where it is in the photo of the Colt when it is zeroed properly, not where it is in the photo of the S&W. A taller front sight post will not solve this problem. The top of the post is where you place the target and it will always be there whether a taller front sight post is used or not. Since my front sight base is an "F" and appears to be the proper height, I have to assume that the problem is that the barrel is slightly canted upward, or there is a problem with the receiver, or some other problem. Anyway, I'm calling S&W because this is unacceptable to me, considering how much I paid for this carbine.
    Last edited by Putter; 02-26-07 at 23:48. Reason: added

  8. #8
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    Quote Originally Posted by Tang419 View Post
    My S&W has an F marked on the side.
    So does mine.

    Does the top of your front sight post also stick way up above the top of the protective"ears", and your rear sight aperture sit far to the right side of the rear sight base when your iron sights are zeroed?
    Last edited by Putter; 02-26-07 at 04:12. Reason: added comments

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    Quote Originally Posted by Mark/MO View Post
    I just measured my S&W front sight base. It is marked with the F and matches the measurements shown above for an F base. While I don't know when it was made I traded for it new in the box back in November. Perhaps this is a recent problem?
    Mine also is marked with the F. But does the top of your front sight post stick up above the top of the protective "ears" too?

  10. #10
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    No, but it is pretty close. Looking at your photos my post does not set nearly as high. I'm not experienced enough to pass judgement on what might cause this. I also saw several posts about windage problems but I have not experienced that. Mine is pretty much centered once zeroed.

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