I have several stainless guns from the early and mid 70s. ALL have had this issue. Became so frustrating, I had a gunsmith secure them with some form of LocTite. Nail polish would not work.

Funny story: 4 years ago, I bought an absolutely NIB 64 pencil barrel, a grail gun for me. When the thumbpiece lug began to work loose while shooting, I felt almost reassured, as though it were an old friend. Seemed as though the 64 had come from a buried "time capsule." Odd, but there it is. Happy New Year!

Kaaskop49
Shield #5103