What do the barrel walls measure? Every Darne at my house, 3 at the moment, is over .050 wall. I’ve measured guns that had .020-.030 thicker walls, too. If the gun saw double or triple proof, when it was a new gun, you might not need to worry too much, if you feed it light hunting loads.

Let’s see a photo of the flats and the tubes where they enter the flats.

Best,
Ted