I have used JB Weld to repair the sealing surface on shafts, repair nicks in hydraulic rams, and for spot putty on rock nicks that go to the metal on my cars. Sand it smooth and paint with spray touch up and it is as good as new. I used a product like JB Weld (Belzona Molecular) to repair a broken trigger about thirty five years ago and it is as good as ever. I added a bit to the back of the trigger so it would hit the trigger guard to act as a stop. (which is what I was trying to do when I broke the trigger).
Slow cure epoxy is good for just about anything where metal is concerned as long as the temp stays below 200 degrees F.
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MILF EBONY