You may already know or have information on inleting or seating a barrel (bedding?).
But you might find this article by Budd Davisson on airbum.com interesting as you think about building your kit, just to get your thought processes going. He mentions a swamped barrel and gives some construction tips that could apply to any build.
Perhaps this type of info is in one of the links given by others....I didn't check them out. I'm know there is lots of good info right here on this forum (Captchee, Wyosmith, searching 'kit building' ect.).
http://www.airbum.com/NeatShtpix/HainesPart3.html
To start at the beginning of this article about building a Kentucky flinter.....
http://www.airbum.com/NeatShtpix/HainesPart1.html
sharp tools + wood = bandaids (at my house)