"Plain Steel" is
not pattern welded steel and was used for a short period in transition from "Decarbonized Steel" or "Bessemer process homogenous wrought iron" which was sourced from Remington
1874 Price List
Plain Steel 1875 12g 0 Grade courtesy of Wally Shayer
I agree with Dave and would not use the barrels with ANY load.
The musket stuff was "Best Gun Iron" on this 1866 Price list
