Sorry for the obtuseness and I'll try again.
Proper evaluation of vintage barrels (steel or Damascus) require direct visualization of the bore. I agree the pits were present on purchase and would have been seen with a bore scope.
"Light to moderate pitting" in the chamber or just past the forcing cones is a different issue than pits in the distal 1/3 of the barrel
Typical superficial pits just past the forcing cone
These erosions would be of concern
Can't know if someone doesn't look, using the proper equipment.
Owen: composition analysis of pattern welded barrels show them to be wrought iron and low carbon, low alloy "mild" steel with a Brinell Hardness level of about 100;
much softer than stainless steel and even a bit less than Phosphor Bronze
http://www.aertesting.com/uploads/3/3/5/8/3358290/bhn_of_various_materials.pdf Hoppe's 9 has a Phosphor bronze brush.
I'd stick with copper and the Big 45 product. It is reported to be "a proprietary alloy containing stainless steel, nickel silver, monel (a corrosion resistant nickel based alloy), and zinc" but is likely mostly (soft) zinc.
