I purchased a rifle with an Unertl scope on it recently, and found that the rear mount has a problem.

The knob that tightens the mount onto the base works by threading onto a screw that is held captive in the aluminum mount opposite the locking knob.  On my mount, the screw has pulled out of the aluminum.  The aluminum is friction welded to the screw till no threads are visible, and I can't remove the knob as the threads are too messed up with the galled aluminum.  I can't see how I can repair this screw.  I might be able to take the aluminum off of it with lye to see if anything is salvageable with the screw.

It appears that the original installation threaded the screw into the aluminum, until it was tight enough to jam.  Now, as you tighten the locking knob, it merely pulls the screw out of the aluminum.

Any ideas on how to repair it?  The options I have thought of are to find a #6 x 40 screw to replace the current one, and thread it into the aluminum and hope it holds.  Or, chemically remove the aluminum from the existing screw and see if I can re-insert it.  Or, pound the screw into the aluminum after coating it with Locktite and hope it holds.

Any suggestions?

dave

Some people have drilled out and threaded for a newly manufactured larger screw.

Thanks for the ideas.  I think the first thing to do is get some lye and dissolve the aluminum off of the screw, so that I can chase the threads if necessary and get the knob off.  Then, I can try various ways to lock the screw or a new one back into the aluminum hole.  One thing that is obvious by looking at it is that the thread is so close to the exterior of the mount that a punch should deform it enough to tighten the hole up.  Some thread forming glue, epoxy, or locktite might aid in that too.

dave

Dave,
Is your problem with the front or rear mount? If its the rear mount and a 3/4? diameter scope, drop me a line at (You need to Login or Register to view media files and links) and I can help you out.