Prior to "Open Hearth" steel, the wrought iron components were scrap horse shoes (Spain) and horse-nail stubs, ox irons; steel, worn scythes, old chain, broken coach-springs, and Soft steel, which is decarbonized in the course of manufacture (likely Bessemer).
The sources of nail stubs were exhausted by the mid-1800s, and in the 1881 3rd Edition of Greener's The Gun he states that scrap iron and steel were no longer being used for barrels.
The 1891 study on page 4 lists structural steel and chain as having .2 - .25 carbon. Vickers was listed as .24 - .27%.


https://sites.google.com/a/damascusknowledge.com/www/home