Rear Sight off to one side

[Dan H.]

Shot my Limited rifle today DPMS upper Mickluk comp. and had to move my rear sight a few clicks to the left. It has always favored that side but now it is real bad only a few clicks of adjustment left. What causes this? The gun still shoots good so is this something to be concerned about. Thanks Dan

[Religious Shooter]

Usually it means the barrel nut wasn't torqued correctly.

But it could be other things.

If you are really concerned about it return it to DPMS or whoever built it. Personally, if it shoots well and it functions who cares.

[George]

Loose barrel nut is possible. Loose gas block allowing front site to move to one side or other is also a possibility. Bent front sight post is another possibility. Rotate front post a quarter turn and see if you get a gross windage POI shift, this would indicate a bent front sight post.

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Regards,

[rhino]

That was (is) a common problem for Bushmaster rifles. They were leaving the factory with the front sight tower improperly indexed. I had to send mine back to the factory to get it fixed.

Could be the same thing with your upper.

[P.E. Kelley]

Check to see if you have DPMS's match front sight base. It will have 4 set screws that are secured against flats milled on the barrel.

Three of mine are so equipped.

PK

[SinistralRifleman]

If your zero is progressively drifting more to one side, sounds like a loose barrel nut to me. If your front sight base is loose, that could be the problem as well.

[Carlos]

Rhino wrote: "They were leaving the factory with the front sight tower improperly indexed. I had to send mine back to the factory to get it fixed."

That mirrors my friend's exact experience in 2004. THe shop where he bought it first swapped out carry handles. Same results. After the complete rifle returned from the factory, the problem was fixed free of charge.

I'd return it under warranty. If its not under warranty and if you have receiver blocks & the wrench, try shimming the barrel index pin to the left-most position.