Actually Dogfox, I only impersonate a metallurgist here on DoubleGun.
I have however spent a lot of personal $s and time studying and discussing vintage gun barrel steels with the engineers at METL. It is quite likely that the "Cast Steel" barrel is Decarbonized steel, but I will know for sure when I have it zapped along with the vintage double frames for composition analysis. Those of us choosing to use ancient and obscure guns might be interested
https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit
I've also researched wall thickness recommendations (see the links above) and have discussed such with gunsmiths. I should have made clear that my recommendation was for vintage doublegun barrel steels.
I'm simply offering an opinion, and interested in opinions of others, including yourself. Please share yours, and the basis for that opinion.