I was working on one of my Webley Ospreys recently, trying to get the loading tap perfectly aligned. It was too far over to the left, so the pellets were clipping as they entered the barrel, giving poor accuracy. I tried various shimming but none worked very well. So since I had nothing to lose, I thought I'd try superglue. I bought some new (it goes off, probably from atmospheric moisture), then coated the inside of the flange with it - being liquid, it forms into a meniscus in the flange. I then left it overnight to set.

Next morning I checked, and the glue had set hard - but how hard, I didn't realize till I tried to sand it! I put the tap in the pillar drill and began cutting the glued flange back with a needle file, which was a slow process, but perfect as it made it very controllable. The glue never tried to break up and come away, it stayed resolutely stuck as if it was now part of the metal, and after a few hours (!) of filing and testing, I got the port aligned and the gun now shoots beautifully.

I've heard of people mixing talc or baking soda with superglue to fill bigger gaps, or even moulding with it, but I was surprised and impressed at how strong it was.