Thanks to all who’ve replied. I’ll try the Loctite, and keep an eye on it.

Seeing a B-SS in an early 70s Browning catalogue as a child was my first glimpse of a side-by-side.... Elmer Fudd’s ever-present double excepted. I’ve had a bee in my bonnet for juxtaposeds in general and the B-SS specifically ever since. Glad I finally have one. The pin-drift issue aside, it’s been as reliable as a brick for the few hundred shells I’ve put through it so far. And the coach at the trap & skeet club said it seems to fit me well. I enjoy busting porcelain frisbees with it. Feels right. When I’m doing it properly, it feels transparent.