Rear sight base and aperture loose

[purple]

You need to replace the rear sight cover. Look for a new one with an intact/unworn inner rib. When assembling the rear sight use rifle grease on the inner rib of the sight cover,the foot and teeth of the aperture,and on the interior bearing ways of the base which contact the aperture. Grease is also required on the receiver where the inner faces of the elevation and windage knobs bear and on the axial holes that the windage and elevation knobs pass through. Final grease point is where the bottom of the base bears against the receiver(you can see the finish wear on the bottom of the base). The grease minimizes wear and friction and helps tighten things up a bit.