Mark: thank you for posting that frightening illustration of the result of misguided and inexpert chamber work. Was the chamber extended also? What is the current chamber length? Researcher has established that at least until 1926 (after introduction of the NID) 20g Ithaca chambers were 2 1/2"
I took the liberty of sharing the story and one image about 1/3 down here
https://docs.google.com/document/d/1...vwLYc-kGA/edit
I do not believe Brad or Kirk would attempt to repair the chamber, but anxiously await the rest of the story. It
might be possible to sleeve the chamber and barrels past the thin area, but as a 20g it would probably need to be to .410.
Fitting a donor 20g fluid steel Flues barrel would likely be much cheaper.
I would also not suggest full length tube inserts in light of the cracked chamber wall.