I bought a 16 gauge LC Smith field grade shotgun a few years ago. It has a three position automatic safety. I looked it up when I bought it and I believe it was manufactured in the 19-teens. I've been using it for grouse and pheasant and love it.

Over the course of the last two seasons, three times the safety has become incredibly stiff. Like I need to use both thumbs and push hard to get the safety to budge. Twice this has "magically" resolved itself. I even had it to a gunsmith (who is familiar with and hunts with LC Smith) to take a look at it but it was not showing the symptom at the time and he couldn't figure anything out.

Is there any wood that could swell up that could cause this, or spot where some rust could show up that would cause this? The fact that it happens and resolves itself is puzzling. Has anyone had an issue like this before?

Many thanks