When I was sighting in my Mini 14 to get the point of aim correct I had to raise the rear sight up. The problem is that the plunger that holds the sight in place doesn't reach the sight. Now when I shoot the sight moves.
Anybody have any idea how to fix this??

What happened is when you were sighting it in you werent centering the post (front sight) properly inside the aperature. which would cause you to adjust the rear sight too high. Lower the rear sight enough that it is in contact with the plunger and hold the post (front sight) a little higher inside the aperature. I have done the same thing in the past when I wasnt used to using an aperature sight. good luck

I have an older one and had that trouble, I finally just filed off a little of the front site and lowered the rear...worked for me!!

Doug