Rear Sight Windage

[flygrimm]

Hey folks

Having an issue with the rear sight on my M1a. When turning the windage clocklwise to move the sight to the right it gets tighter the further right it goes. Once you are pretty close to the end it is very difficult to move. The opposite is true when moving the sight base to the left. The further left it gets the easier it gets so much so that when the sight is close to center it will not click anymore, it just turns and moves the sight.

Springfield Receiver.
There is a small hole in the receiver on the windage side at about the 4 o'clock position.
Windage knob is marked LPR NM and has 4 'bumps' on the face that goes against the receiver.
Elevation knob is marked with an M and FZR.
Sight base is marked NM/2A (not sure about that last one it is difficult to read).

Any suggestions?

Thanks

Stuart

Information

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[browningautorifle]

Could you take some pics and show us? It's hard to see what's happening here...

[The Lemming]

I'm by no means an expert, but IIRC there should be a ball bearing in that 4 o'clock hole in the receiver you mention. Some NM sights use the ball bearing and detents in the rear sight base to give you the 1/2 minute NM adjustments.

The other way to do it is a sight base and windage knob with a thread pitch cut to give you the 1/2 minute adjustment.

If I'm wrong I'm sure someone else will set us both straight. LOL

[RCS]

sounds like the Air Force match rifle rear sight assembly with the ball bearing and spring ?

[flygrimm]

Attachment 68630Attachment 68631

Ok. Pics. First is the back side of the windage knob. Second is the RH side showing the hole. It is shaped like a ball would fit in it but no room for a spring behind.

More info. The receiver is a commercial Springfield manufactured in 1990. You can get the rear sight to 'click' when the sight is left of center by tightening the nut in the center of the windage knob but then when you move the sight right of center it becomes very tight and then is so tight it won't move. Also if the nut is tightened like this the elevation locks up.

Stuart

[browningautorifle]

Is the spring present in the windage knob? If it's bound up it will fetch up like you describe. You may just need a new knob. And by nut, you mean screw, yes?

[flygrimm]

Is the spring present in the windage knob? If it's bound up it will fetch up like you describe. You may just need a new knob. And by nut, you mean screw, yes?

I would think the screw is the part attached to the elevation knob and the nut is the part in the center of the windage knob, but you have to use a screwdriver instead of a wrench to tighten it. As far as I can tell the spring is built into the elevation knob. There is no spring in the windage knob (the one pictured).

Try to replace the elevation knob assembly?

Stuart

[fjruple]

Hi Stuart--

It look like your SAI rear sight which used the ball and detent was replaced with a regular NM rear sight. The two issues often associated with replacement with a NM rear sight is: Commercial aftermarket NM rear sights are not heat treated for hardness and wear out faster. The other problem is the NM rear sights are not properly fitted to the rifle. If you don't know already the pitch of the threads on the NM base and NM windage knob are different than the standard sight base and windage knob.

My 2 cents

--fjruple

---------- Post added at 07:29 AM ---------- Previous post was at 07:27 AM ----------

Stuart--

The spring for tension in the windage knob is in the Elevation knob.

--fjruple

[browningautorifle]

screw is the part attached to the elevation knob

Right, all that is right. The inside is where you think the problem is then? Have you tried a replacement set on this rifle?

[flygrimm]

Right, all that is right. The inside is where you think the problem is then? Have you tried a replacement set on this rifle?

Going to order a new elevation knob assembly and see if that cures it. I have a feeling the spring is bunged up. Will let you know results when I get it. Should be a week or so.

Stuart