What can I use to protect the metal-to-wood inlet surfaces and barrel channel on a rifle I plan to hunt with?
Applying a coat or two of whatever finish was used on the rest of the gun to the inlet surfaces helps protect them, and the bottom of the barrel channel can be waxed, oiled, or lightly greased. Original guns were not perfectly sealed in these areas either and still saw hard service, so it is not something to be overly concerned about.