Drew & KY Jon,
They are fluid steel. Minimum dimensions start 8-9 inches forward of the breechface and run consistent to the chokes. Bores measure .615"/.616 just forward of forcing cones and just before chokes. 28" Mod & Full. 2-1/2" chambers. Weight is 5lb-9oz.
Ky Jon,
I don't reload any shot shells anymore. I have reloaded for rifles since 1976 and still have all my equipment. I was heavy into benchrest shooting and KNOW the finesse involved. I have flats of 2-1/2" Polywad Vintagers in 20, 16, and 12 ga and also 2-3/4" Win AA low recoil/pressure in 12 & 20 ga. But I have never had another gun with tubes this thin.
John