I was kind of wondering about that decimal point also. Great picture also Doc Drew, possibly higher magnification than 20x. Do the folks at the lab think that's a view of the grain in the steel component.

Seems most of Adam's comments were about inclusions, with none of them likely to contribute to the strength of the barrel. I'd still wonder if the labor was put in to overcome the shortcomings of the material.

Maybe, mono steels needed to be reliable and cost effective before taking over. Might be too that alloying became more important than just upping the carbon percentage.