Hello all. I recently acquired a Chapuis Express Rifle in 8x57 JRS caliber. Perhaps some of you double rifle enthusiasts can help me. This rifle is used, and I would guess at least 20 years old, but used very little.

1. It is locked closed. The top lever moves fine and feels like it is pushing against a spring, which is normal, but the action does not open up at all, not at all.
I don't think this is a firing pin problem, since it does not open even a little bit. To me it acts like the action locking wedge or whatever it has, is stuck into the barrel lumps. Or, maybe whatever mechanism is supposed to pull the locking wedge out of the barrel lumps has broken.
I squirted a bit of high-quality lube inside, let it soak a bit, and tried it again, no go. I also tried opening the rifle with the rifle upside down and different angles, and even hit the buttplate with the palm of my hand in case it is some kind of inertia issue, nothing worked.
Any ideas please. It seems I may have to take it to a qualified gunsmith.

2. It has pivot type scope bases. I have learned these can be rather specialized, and also expansive. Have any of you replaced these bases with more flexible bases, perhaps Picatinny or Weaver type or some other?

Thank you,
Arthur
Michigan, USA