OK. Was thinking and typing before the length of the F.C. clarification. .076" at 10" is certainly adequate.
And I agree with Edgar that these looooooong cones are the result of honing; pitting is usually worse into and just past the cones.
Looking toward the breech from just past the cones (barrel has been cut)
Again - please confirm the forward end-of-the-chamber WT, and please let Mr. Fey know that the "end-of-the-chamber" recommendation of .105" is the forward end; not the breech end.
And BTW: .200-.210" is typical breech WT for U.S. 12g chambers