Norc M4 Rear sight wobble

[bluemike807]

Just bought a used Norc M4 and noticed that the rear sight on the standard carry handle is very loose - almost feels spring loaded, but can easily be rotated side to side a few degrees.

How do I fix this?

 

[Ganderite]

If it springs back to the same position each time, it is less of an issue.

I do not know how to tighten it.